1 // SPDX-License-Identifier: GPL-2.0
3 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
5 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
7 * Interactivity improvements by Mike Galbraith
8 * (C) 2007 Mike Galbraith <efault@gmx.de>
10 * Various enhancements by Dmitry Adamushko.
11 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
13 * Group scheduling enhancements by Srivatsa Vaddagiri
14 * Copyright IBM Corporation, 2007
15 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
17 * Scaled math optimizations by Thomas Gleixner
18 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
20 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
21 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
26 * Targeted preemption latency for CPU-bound tasks:
28 * NOTE: this latency value is not the same as the concept of
29 * 'timeslice length' - timeslices in CFS are of variable length
30 * and have no persistent notion like in traditional, time-slice
31 * based scheduling concepts.
33 * (to see the precise effective timeslice length of your workload,
34 * run vmstat and monitor the context-switches (cs) field)
36 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
38 unsigned int sysctl_sched_latency
= 6000000ULL;
39 static unsigned int normalized_sysctl_sched_latency
= 6000000ULL;
42 * The initial- and re-scaling of tunables is configurable
46 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
47 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
48 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
50 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
52 unsigned int sysctl_sched_tunable_scaling
= SCHED_TUNABLESCALING_LOG
;
55 * Minimal preemption granularity for CPU-bound tasks:
57 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
59 unsigned int sysctl_sched_min_granularity
= 750000ULL;
60 static unsigned int normalized_sysctl_sched_min_granularity
= 750000ULL;
63 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
65 static unsigned int sched_nr_latency
= 8;
68 * After fork, child runs first. If set to 0 (default) then
69 * parent will (try to) run first.
71 unsigned int sysctl_sched_child_runs_first __read_mostly
;
74 * SCHED_OTHER wake-up granularity.
76 * This option delays the preemption effects of decoupled workloads
77 * and reduces their over-scheduling. Synchronous workloads will still
78 * have immediate wakeup/sleep latencies.
80 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
82 unsigned int sysctl_sched_wakeup_granularity
= 1000000UL;
83 static unsigned int normalized_sysctl_sched_wakeup_granularity
= 1000000UL;
85 const_debug
unsigned int sysctl_sched_migration_cost
= 500000UL;
87 int sched_thermal_decay_shift
;
88 static int __init
setup_sched_thermal_decay_shift(char *str
)
92 if (kstrtoint(str
, 0, &_shift
))
93 pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
95 sched_thermal_decay_shift
= clamp(_shift
, 0, 10);
98 __setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift
);
102 * For asym packing, by default the lower numbered CPU has higher priority.
104 int __weak
arch_asym_cpu_priority(int cpu
)
110 * The margin used when comparing utilization with CPU capacity.
114 #define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024)
117 * The margin used when comparing CPU capacities.
118 * is 'cap1' noticeably greater than 'cap2'
122 #define capacity_greater(cap1, cap2) ((cap1) * 1024 > (cap2) * 1078)
125 #ifdef CONFIG_CFS_BANDWIDTH
127 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
128 * each time a cfs_rq requests quota.
130 * Note: in the case that the slice exceeds the runtime remaining (either due
131 * to consumption or the quota being specified to be smaller than the slice)
132 * we will always only issue the remaining available time.
134 * (default: 5 msec, units: microseconds)
136 unsigned int sysctl_sched_cfs_bandwidth_slice
= 5000UL;
139 static inline void update_load_add(struct load_weight
*lw
, unsigned long inc
)
145 static inline void update_load_sub(struct load_weight
*lw
, unsigned long dec
)
151 static inline void update_load_set(struct load_weight
*lw
, unsigned long w
)
158 * Increase the granularity value when there are more CPUs,
159 * because with more CPUs the 'effective latency' as visible
160 * to users decreases. But the relationship is not linear,
161 * so pick a second-best guess by going with the log2 of the
164 * This idea comes from the SD scheduler of Con Kolivas:
166 static unsigned int get_update_sysctl_factor(void)
168 unsigned int cpus
= min_t(unsigned int, num_online_cpus(), 8);
171 switch (sysctl_sched_tunable_scaling
) {
172 case SCHED_TUNABLESCALING_NONE
:
175 case SCHED_TUNABLESCALING_LINEAR
:
178 case SCHED_TUNABLESCALING_LOG
:
180 factor
= 1 + ilog2(cpus
);
187 static void update_sysctl(void)
189 unsigned int factor
= get_update_sysctl_factor();
191 #define SET_SYSCTL(name) \
192 (sysctl_##name = (factor) * normalized_sysctl_##name)
193 SET_SYSCTL(sched_min_granularity
);
194 SET_SYSCTL(sched_latency
);
195 SET_SYSCTL(sched_wakeup_granularity
);
199 void __init
sched_init_granularity(void)
204 #define WMULT_CONST (~0U)
205 #define WMULT_SHIFT 32
207 static void __update_inv_weight(struct load_weight
*lw
)
211 if (likely(lw
->inv_weight
))
214 w
= scale_load_down(lw
->weight
);
216 if (BITS_PER_LONG
> 32 && unlikely(w
>= WMULT_CONST
))
218 else if (unlikely(!w
))
219 lw
->inv_weight
= WMULT_CONST
;
221 lw
->inv_weight
= WMULT_CONST
/ w
;
225 * delta_exec * weight / lw.weight
227 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
229 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
230 * we're guaranteed shift stays positive because inv_weight is guaranteed to
231 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
233 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
234 * weight/lw.weight <= 1, and therefore our shift will also be positive.
236 static u64
__calc_delta(u64 delta_exec
, unsigned long weight
, struct load_weight
*lw
)
238 u64 fact
= scale_load_down(weight
);
239 u32 fact_hi
= (u32
)(fact
>> 32);
240 int shift
= WMULT_SHIFT
;
243 __update_inv_weight(lw
);
245 if (unlikely(fact_hi
)) {
251 fact
= mul_u32_u32(fact
, lw
->inv_weight
);
253 fact_hi
= (u32
)(fact
>> 32);
260 return mul_u64_u32_shr(delta_exec
, fact
, shift
);
264 const struct sched_class fair_sched_class
;
266 /**************************************************************
267 * CFS operations on generic schedulable entities:
270 #ifdef CONFIG_FAIR_GROUP_SCHED
271 static inline struct task_struct
*task_of(struct sched_entity
*se
)
273 SCHED_WARN_ON(!entity_is_task(se
));
274 return container_of(se
, struct task_struct
, se
);
277 /* Walk up scheduling entities hierarchy */
278 #define for_each_sched_entity(se) \
279 for (; se; se = se->parent)
281 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
286 /* runqueue on which this entity is (to be) queued */
287 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
292 /* runqueue "owned" by this group */
293 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
298 static inline void cfs_rq_tg_path(struct cfs_rq
*cfs_rq
, char *path
, int len
)
303 if (cfs_rq
&& task_group_is_autogroup(cfs_rq
->tg
))
304 autogroup_path(cfs_rq
->tg
, path
, len
);
305 else if (cfs_rq
&& cfs_rq
->tg
->css
.cgroup
)
306 cgroup_path(cfs_rq
->tg
->css
.cgroup
, path
, len
);
308 strlcpy(path
, "(null)", len
);
311 static inline bool list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
313 struct rq
*rq
= rq_of(cfs_rq
);
314 int cpu
= cpu_of(rq
);
317 return rq
->tmp_alone_branch
== &rq
->leaf_cfs_rq_list
;
322 * Ensure we either appear before our parent (if already
323 * enqueued) or force our parent to appear after us when it is
324 * enqueued. The fact that we always enqueue bottom-up
325 * reduces this to two cases and a special case for the root
326 * cfs_rq. Furthermore, it also means that we will always reset
327 * tmp_alone_branch either when the branch is connected
328 * to a tree or when we reach the top of the tree
330 if (cfs_rq
->tg
->parent
&&
331 cfs_rq
->tg
->parent
->cfs_rq
[cpu
]->on_list
) {
333 * If parent is already on the list, we add the child
334 * just before. Thanks to circular linked property of
335 * the list, this means to put the child at the tail
336 * of the list that starts by parent.
338 list_add_tail_rcu(&cfs_rq
->leaf_cfs_rq_list
,
339 &(cfs_rq
->tg
->parent
->cfs_rq
[cpu
]->leaf_cfs_rq_list
));
341 * The branch is now connected to its tree so we can
342 * reset tmp_alone_branch to the beginning of the
345 rq
->tmp_alone_branch
= &rq
->leaf_cfs_rq_list
;
349 if (!cfs_rq
->tg
->parent
) {
351 * cfs rq without parent should be put
352 * at the tail of the list.
354 list_add_tail_rcu(&cfs_rq
->leaf_cfs_rq_list
,
355 &rq
->leaf_cfs_rq_list
);
357 * We have reach the top of a tree so we can reset
358 * tmp_alone_branch to the beginning of the list.
360 rq
->tmp_alone_branch
= &rq
->leaf_cfs_rq_list
;
365 * The parent has not already been added so we want to
366 * make sure that it will be put after us.
367 * tmp_alone_branch points to the begin of the branch
368 * where we will add parent.
370 list_add_rcu(&cfs_rq
->leaf_cfs_rq_list
, rq
->tmp_alone_branch
);
372 * update tmp_alone_branch to points to the new begin
375 rq
->tmp_alone_branch
= &cfs_rq
->leaf_cfs_rq_list
;
379 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
381 if (cfs_rq
->on_list
) {
382 struct rq
*rq
= rq_of(cfs_rq
);
385 * With cfs_rq being unthrottled/throttled during an enqueue,
386 * it can happen the tmp_alone_branch points the a leaf that
387 * we finally want to del. In this case, tmp_alone_branch moves
388 * to the prev element but it will point to rq->leaf_cfs_rq_list
389 * at the end of the enqueue.
391 if (rq
->tmp_alone_branch
== &cfs_rq
->leaf_cfs_rq_list
)
392 rq
->tmp_alone_branch
= cfs_rq
->leaf_cfs_rq_list
.prev
;
394 list_del_rcu(&cfs_rq
->leaf_cfs_rq_list
);
399 static inline void assert_list_leaf_cfs_rq(struct rq
*rq
)
401 SCHED_WARN_ON(rq
->tmp_alone_branch
!= &rq
->leaf_cfs_rq_list
);
404 /* Iterate thr' all leaf cfs_rq's on a runqueue */
405 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
406 list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \
409 /* Do the two (enqueued) entities belong to the same group ? */
410 static inline struct cfs_rq
*
411 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
413 if (se
->cfs_rq
== pse
->cfs_rq
)
419 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
425 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
427 int se_depth
, pse_depth
;
430 * preemption test can be made between sibling entities who are in the
431 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
432 * both tasks until we find their ancestors who are siblings of common
436 /* First walk up until both entities are at same depth */
437 se_depth
= (*se
)->depth
;
438 pse_depth
= (*pse
)->depth
;
440 while (se_depth
> pse_depth
) {
442 *se
= parent_entity(*se
);
445 while (pse_depth
> se_depth
) {
447 *pse
= parent_entity(*pse
);
450 while (!is_same_group(*se
, *pse
)) {
451 *se
= parent_entity(*se
);
452 *pse
= parent_entity(*pse
);
456 #else /* !CONFIG_FAIR_GROUP_SCHED */
458 static inline struct task_struct
*task_of(struct sched_entity
*se
)
460 return container_of(se
, struct task_struct
, se
);
463 #define for_each_sched_entity(se) \
464 for (; se; se = NULL)
466 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
468 return &task_rq(p
)->cfs
;
471 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
473 struct task_struct
*p
= task_of(se
);
474 struct rq
*rq
= task_rq(p
);
479 /* runqueue "owned" by this group */
480 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
485 static inline void cfs_rq_tg_path(struct cfs_rq
*cfs_rq
, char *path
, int len
)
488 strlcpy(path
, "(null)", len
);
491 static inline bool list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
496 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
500 static inline void assert_list_leaf_cfs_rq(struct rq
*rq
)
504 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
505 for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
507 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
513 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
517 #endif /* CONFIG_FAIR_GROUP_SCHED */
519 static __always_inline
520 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
);
522 /**************************************************************
523 * Scheduling class tree data structure manipulation methods:
526 static inline u64
max_vruntime(u64 max_vruntime
, u64 vruntime
)
528 s64 delta
= (s64
)(vruntime
- max_vruntime
);
530 max_vruntime
= vruntime
;
535 static inline u64
min_vruntime(u64 min_vruntime
, u64 vruntime
)
537 s64 delta
= (s64
)(vruntime
- min_vruntime
);
539 min_vruntime
= vruntime
;
544 static inline bool entity_before(struct sched_entity
*a
,
545 struct sched_entity
*b
)
547 return (s64
)(a
->vruntime
- b
->vruntime
) < 0;
550 #define __node_2_se(node) \
551 rb_entry((node), struct sched_entity, run_node)
553 static void update_min_vruntime(struct cfs_rq
*cfs_rq
)
555 struct sched_entity
*curr
= cfs_rq
->curr
;
556 struct rb_node
*leftmost
= rb_first_cached(&cfs_rq
->tasks_timeline
);
558 u64 vruntime
= cfs_rq
->min_vruntime
;
562 vruntime
= curr
->vruntime
;
567 if (leftmost
) { /* non-empty tree */
568 struct sched_entity
*se
= __node_2_se(leftmost
);
571 vruntime
= se
->vruntime
;
573 vruntime
= min_vruntime(vruntime
, se
->vruntime
);
576 /* ensure we never gain time by being placed backwards. */
577 cfs_rq
->min_vruntime
= max_vruntime(cfs_rq
->min_vruntime
, vruntime
);
580 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
584 static inline bool __entity_less(struct rb_node
*a
, const struct rb_node
*b
)
586 return entity_before(__node_2_se(a
), __node_2_se(b
));
590 * Enqueue an entity into the rb-tree:
592 static void __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
594 rb_add_cached(&se
->run_node
, &cfs_rq
->tasks_timeline
, __entity_less
);
597 static void __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
599 rb_erase_cached(&se
->run_node
, &cfs_rq
->tasks_timeline
);
602 struct sched_entity
*__pick_first_entity(struct cfs_rq
*cfs_rq
)
604 struct rb_node
*left
= rb_first_cached(&cfs_rq
->tasks_timeline
);
609 return __node_2_se(left
);
612 static struct sched_entity
*__pick_next_entity(struct sched_entity
*se
)
614 struct rb_node
*next
= rb_next(&se
->run_node
);
619 return __node_2_se(next
);
622 #ifdef CONFIG_SCHED_DEBUG
623 struct sched_entity
*__pick_last_entity(struct cfs_rq
*cfs_rq
)
625 struct rb_node
*last
= rb_last(&cfs_rq
->tasks_timeline
.rb_root
);
630 return __node_2_se(last
);
633 /**************************************************************
634 * Scheduling class statistics methods:
637 int sched_update_scaling(void)
639 unsigned int factor
= get_update_sysctl_factor();
641 sched_nr_latency
= DIV_ROUND_UP(sysctl_sched_latency
,
642 sysctl_sched_min_granularity
);
644 #define WRT_SYSCTL(name) \
645 (normalized_sysctl_##name = sysctl_##name / (factor))
646 WRT_SYSCTL(sched_min_granularity
);
647 WRT_SYSCTL(sched_latency
);
648 WRT_SYSCTL(sched_wakeup_granularity
);
658 static inline u64
calc_delta_fair(u64 delta
, struct sched_entity
*se
)
660 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
661 delta
= __calc_delta(delta
, NICE_0_LOAD
, &se
->load
);
667 * The idea is to set a period in which each task runs once.
669 * When there are too many tasks (sched_nr_latency) we have to stretch
670 * this period because otherwise the slices get too small.
672 * p = (nr <= nl) ? l : l*nr/nl
674 static u64
__sched_period(unsigned long nr_running
)
676 if (unlikely(nr_running
> sched_nr_latency
))
677 return nr_running
* sysctl_sched_min_granularity
;
679 return sysctl_sched_latency
;
683 * We calculate the wall-time slice from the period by taking a part
684 * proportional to the weight.
688 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
690 unsigned int nr_running
= cfs_rq
->nr_running
;
693 if (sched_feat(ALT_PERIOD
))
694 nr_running
= rq_of(cfs_rq
)->cfs
.h_nr_running
;
696 slice
= __sched_period(nr_running
+ !se
->on_rq
);
698 for_each_sched_entity(se
) {
699 struct load_weight
*load
;
700 struct load_weight lw
;
702 cfs_rq
= cfs_rq_of(se
);
703 load
= &cfs_rq
->load
;
705 if (unlikely(!se
->on_rq
)) {
708 update_load_add(&lw
, se
->load
.weight
);
711 slice
= __calc_delta(slice
, se
->load
.weight
, load
);
714 if (sched_feat(BASE_SLICE
))
715 slice
= max(slice
, (u64
)sysctl_sched_min_granularity
);
721 * We calculate the vruntime slice of a to-be-inserted task.
725 static u64
sched_vslice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
727 return calc_delta_fair(sched_slice(cfs_rq
, se
), se
);
733 static int select_idle_sibling(struct task_struct
*p
, int prev_cpu
, int cpu
);
734 static unsigned long task_h_load(struct task_struct
*p
);
735 static unsigned long capacity_of(int cpu
);
737 /* Give new sched_entity start runnable values to heavy its load in infant time */
738 void init_entity_runnable_average(struct sched_entity
*se
)
740 struct sched_avg
*sa
= &se
->avg
;
742 memset(sa
, 0, sizeof(*sa
));
745 * Tasks are initialized with full load to be seen as heavy tasks until
746 * they get a chance to stabilize to their real load level.
747 * Group entities are initialized with zero load to reflect the fact that
748 * nothing has been attached to the task group yet.
750 if (entity_is_task(se
))
751 sa
->load_avg
= scale_load_down(se
->load
.weight
);
753 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
756 static void attach_entity_cfs_rq(struct sched_entity
*se
);
759 * With new tasks being created, their initial util_avgs are extrapolated
760 * based on the cfs_rq's current util_avg:
762 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
764 * However, in many cases, the above util_avg does not give a desired
765 * value. Moreover, the sum of the util_avgs may be divergent, such
766 * as when the series is a harmonic series.
768 * To solve this problem, we also cap the util_avg of successive tasks to
769 * only 1/2 of the left utilization budget:
771 * util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
773 * where n denotes the nth task and cpu_scale the CPU capacity.
775 * For example, for a CPU with 1024 of capacity, a simplest series from
776 * the beginning would be like:
778 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
779 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
781 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
782 * if util_avg > util_avg_cap.
784 void post_init_entity_util_avg(struct task_struct
*p
)
786 struct sched_entity
*se
= &p
->se
;
787 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
788 struct sched_avg
*sa
= &se
->avg
;
789 long cpu_scale
= arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq
)));
790 long cap
= (long)(cpu_scale
- cfs_rq
->avg
.util_avg
) / 2;
793 if (cfs_rq
->avg
.util_avg
!= 0) {
794 sa
->util_avg
= cfs_rq
->avg
.util_avg
* se
->load
.weight
;
795 sa
->util_avg
/= (cfs_rq
->avg
.load_avg
+ 1);
797 if (sa
->util_avg
> cap
)
804 sa
->runnable_avg
= sa
->util_avg
;
806 if (p
->sched_class
!= &fair_sched_class
) {
808 * For !fair tasks do:
810 update_cfs_rq_load_avg(now, cfs_rq);
811 attach_entity_load_avg(cfs_rq, se);
812 switched_from_fair(rq, p);
814 * such that the next switched_to_fair() has the
817 se
->avg
.last_update_time
= cfs_rq_clock_pelt(cfs_rq
);
821 attach_entity_cfs_rq(se
);
824 #else /* !CONFIG_SMP */
825 void init_entity_runnable_average(struct sched_entity
*se
)
828 void post_init_entity_util_avg(struct task_struct
*p
)
831 static void update_tg_load_avg(struct cfs_rq
*cfs_rq
)
834 #endif /* CONFIG_SMP */
837 * Update the current task's runtime statistics.
839 static void update_curr(struct cfs_rq
*cfs_rq
)
841 struct sched_entity
*curr
= cfs_rq
->curr
;
842 u64 now
= rq_clock_task(rq_of(cfs_rq
));
848 delta_exec
= now
- curr
->exec_start
;
849 if (unlikely((s64
)delta_exec
<= 0))
852 curr
->exec_start
= now
;
854 schedstat_set(curr
->statistics
.exec_max
,
855 max(delta_exec
, curr
->statistics
.exec_max
));
857 curr
->sum_exec_runtime
+= delta_exec
;
858 schedstat_add(cfs_rq
->exec_clock
, delta_exec
);
860 curr
->vruntime
+= calc_delta_fair(delta_exec
, curr
);
861 update_min_vruntime(cfs_rq
);
863 if (entity_is_task(curr
)) {
864 struct task_struct
*curtask
= task_of(curr
);
866 trace_sched_stat_runtime(curtask
, delta_exec
, curr
->vruntime
);
867 cgroup_account_cputime(curtask
, delta_exec
);
868 account_group_exec_runtime(curtask
, delta_exec
);
871 account_cfs_rq_runtime(cfs_rq
, delta_exec
);
874 static void update_curr_fair(struct rq
*rq
)
876 update_curr(cfs_rq_of(&rq
->curr
->se
));
880 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
882 u64 wait_start
, prev_wait_start
;
884 if (!schedstat_enabled())
887 wait_start
= rq_clock(rq_of(cfs_rq
));
888 prev_wait_start
= schedstat_val(se
->statistics
.wait_start
);
890 if (entity_is_task(se
) && task_on_rq_migrating(task_of(se
)) &&
891 likely(wait_start
> prev_wait_start
))
892 wait_start
-= prev_wait_start
;
894 __schedstat_set(se
->statistics
.wait_start
, wait_start
);
898 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
900 struct task_struct
*p
;
903 if (!schedstat_enabled())
907 * When the sched_schedstat changes from 0 to 1, some sched se
908 * maybe already in the runqueue, the se->statistics.wait_start
909 * will be 0.So it will let the delta wrong. We need to avoid this
912 if (unlikely(!schedstat_val(se
->statistics
.wait_start
)))
915 delta
= rq_clock(rq_of(cfs_rq
)) - schedstat_val(se
->statistics
.wait_start
);
917 if (entity_is_task(se
)) {
919 if (task_on_rq_migrating(p
)) {
921 * Preserve migrating task's wait time so wait_start
922 * time stamp can be adjusted to accumulate wait time
923 * prior to migration.
925 __schedstat_set(se
->statistics
.wait_start
, delta
);
928 trace_sched_stat_wait(p
, delta
);
931 __schedstat_set(se
->statistics
.wait_max
,
932 max(schedstat_val(se
->statistics
.wait_max
), delta
));
933 __schedstat_inc(se
->statistics
.wait_count
);
934 __schedstat_add(se
->statistics
.wait_sum
, delta
);
935 __schedstat_set(se
->statistics
.wait_start
, 0);
939 update_stats_enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
941 struct task_struct
*tsk
= NULL
;
942 u64 sleep_start
, block_start
;
944 if (!schedstat_enabled())
947 sleep_start
= schedstat_val(se
->statistics
.sleep_start
);
948 block_start
= schedstat_val(se
->statistics
.block_start
);
950 if (entity_is_task(se
))
954 u64 delta
= rq_clock(rq_of(cfs_rq
)) - sleep_start
;
959 if (unlikely(delta
> schedstat_val(se
->statistics
.sleep_max
)))
960 __schedstat_set(se
->statistics
.sleep_max
, delta
);
962 __schedstat_set(se
->statistics
.sleep_start
, 0);
963 __schedstat_add(se
->statistics
.sum_sleep_runtime
, delta
);
966 account_scheduler_latency(tsk
, delta
>> 10, 1);
967 trace_sched_stat_sleep(tsk
, delta
);
971 u64 delta
= rq_clock(rq_of(cfs_rq
)) - block_start
;
976 if (unlikely(delta
> schedstat_val(se
->statistics
.block_max
)))
977 __schedstat_set(se
->statistics
.block_max
, delta
);
979 __schedstat_set(se
->statistics
.block_start
, 0);
980 __schedstat_add(se
->statistics
.sum_sleep_runtime
, delta
);
983 if (tsk
->in_iowait
) {
984 __schedstat_add(se
->statistics
.iowait_sum
, delta
);
985 __schedstat_inc(se
->statistics
.iowait_count
);
986 trace_sched_stat_iowait(tsk
, delta
);
989 trace_sched_stat_blocked(tsk
, delta
);
992 * Blocking time is in units of nanosecs, so shift by
993 * 20 to get a milliseconds-range estimation of the
994 * amount of time that the task spent sleeping:
996 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
997 profile_hits(SLEEP_PROFILING
,
998 (void *)get_wchan(tsk
),
1001 account_scheduler_latency(tsk
, delta
>> 10, 0);
1007 * Task is being enqueued - update stats:
1010 update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
1012 if (!schedstat_enabled())
1016 * Are we enqueueing a waiting task? (for current tasks
1017 * a dequeue/enqueue event is a NOP)
1019 if (se
!= cfs_rq
->curr
)
1020 update_stats_wait_start(cfs_rq
, se
);
1022 if (flags
& ENQUEUE_WAKEUP
)
1023 update_stats_enqueue_sleeper(cfs_rq
, se
);
1027 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
1030 if (!schedstat_enabled())
1034 * Mark the end of the wait period if dequeueing a
1037 if (se
!= cfs_rq
->curr
)
1038 update_stats_wait_end(cfs_rq
, se
);
1040 if ((flags
& DEQUEUE_SLEEP
) && entity_is_task(se
)) {
1041 struct task_struct
*tsk
= task_of(se
);
1043 if (tsk
->state
& TASK_INTERRUPTIBLE
)
1044 __schedstat_set(se
->statistics
.sleep_start
,
1045 rq_clock(rq_of(cfs_rq
)));
1046 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
1047 __schedstat_set(se
->statistics
.block_start
,
1048 rq_clock(rq_of(cfs_rq
)));
1053 * We are picking a new current task - update its stats:
1056 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
1059 * We are starting a new run period:
1061 se
->exec_start
= rq_clock_task(rq_of(cfs_rq
));
1064 /**************************************************
1065 * Scheduling class queueing methods:
1068 #ifdef CONFIG_NUMA_BALANCING
1070 * Approximate time to scan a full NUMA task in ms. The task scan period is
1071 * calculated based on the tasks virtual memory size and
1072 * numa_balancing_scan_size.
1074 unsigned int sysctl_numa_balancing_scan_period_min
= 1000;
1075 unsigned int sysctl_numa_balancing_scan_period_max
= 60000;
1077 /* Portion of address space to scan in MB */
1078 unsigned int sysctl_numa_balancing_scan_size
= 256;
1080 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
1081 unsigned int sysctl_numa_balancing_scan_delay
= 1000;
1084 refcount_t refcount
;
1086 spinlock_t lock
; /* nr_tasks, tasks */
1091 struct rcu_head rcu
;
1092 unsigned long total_faults
;
1093 unsigned long max_faults_cpu
;
1095 * Faults_cpu is used to decide whether memory should move
1096 * towards the CPU. As a consequence, these stats are weighted
1097 * more by CPU use than by memory faults.
1099 unsigned long *faults_cpu
;
1100 unsigned long faults
[];
1104 * For functions that can be called in multiple contexts that permit reading
1105 * ->numa_group (see struct task_struct for locking rules).
1107 static struct numa_group
*deref_task_numa_group(struct task_struct
*p
)
1109 return rcu_dereference_check(p
->numa_group
, p
== current
||
1110 (lockdep_is_held(&task_rq(p
)->lock
) && !READ_ONCE(p
->on_cpu
)));
1113 static struct numa_group
*deref_curr_numa_group(struct task_struct
*p
)
1115 return rcu_dereference_protected(p
->numa_group
, p
== current
);
1118 static inline unsigned long group_faults_priv(struct numa_group
*ng
);
1119 static inline unsigned long group_faults_shared(struct numa_group
*ng
);
1121 static unsigned int task_nr_scan_windows(struct task_struct
*p
)
1123 unsigned long rss
= 0;
1124 unsigned long nr_scan_pages
;
1127 * Calculations based on RSS as non-present and empty pages are skipped
1128 * by the PTE scanner and NUMA hinting faults should be trapped based
1131 nr_scan_pages
= sysctl_numa_balancing_scan_size
<< (20 - PAGE_SHIFT
);
1132 rss
= get_mm_rss(p
->mm
);
1134 rss
= nr_scan_pages
;
1136 rss
= round_up(rss
, nr_scan_pages
);
1137 return rss
/ nr_scan_pages
;
1140 /* For sanity's sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
1141 #define MAX_SCAN_WINDOW 2560
1143 static unsigned int task_scan_min(struct task_struct
*p
)
1145 unsigned int scan_size
= READ_ONCE(sysctl_numa_balancing_scan_size
);
1146 unsigned int scan
, floor
;
1147 unsigned int windows
= 1;
1149 if (scan_size
< MAX_SCAN_WINDOW
)
1150 windows
= MAX_SCAN_WINDOW
/ scan_size
;
1151 floor
= 1000 / windows
;
1153 scan
= sysctl_numa_balancing_scan_period_min
/ task_nr_scan_windows(p
);
1154 return max_t(unsigned int, floor
, scan
);
1157 static unsigned int task_scan_start(struct task_struct
*p
)
1159 unsigned long smin
= task_scan_min(p
);
1160 unsigned long period
= smin
;
1161 struct numa_group
*ng
;
1163 /* Scale the maximum scan period with the amount of shared memory. */
1165 ng
= rcu_dereference(p
->numa_group
);
1167 unsigned long shared
= group_faults_shared(ng
);
1168 unsigned long private = group_faults_priv(ng
);
1170 period
*= refcount_read(&ng
->refcount
);
1171 period
*= shared
+ 1;
1172 period
/= private + shared
+ 1;
1176 return max(smin
, period
);
1179 static unsigned int task_scan_max(struct task_struct
*p
)
1181 unsigned long smin
= task_scan_min(p
);
1183 struct numa_group
*ng
;
1185 /* Watch for min being lower than max due to floor calculations */
1186 smax
= sysctl_numa_balancing_scan_period_max
/ task_nr_scan_windows(p
);
1188 /* Scale the maximum scan period with the amount of shared memory. */
1189 ng
= deref_curr_numa_group(p
);
1191 unsigned long shared
= group_faults_shared(ng
);
1192 unsigned long private = group_faults_priv(ng
);
1193 unsigned long period
= smax
;
1195 period
*= refcount_read(&ng
->refcount
);
1196 period
*= shared
+ 1;
1197 period
/= private + shared
+ 1;
1199 smax
= max(smax
, period
);
1202 return max(smin
, smax
);
1205 static void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
1207 rq
->nr_numa_running
+= (p
->numa_preferred_nid
!= NUMA_NO_NODE
);
1208 rq
->nr_preferred_running
+= (p
->numa_preferred_nid
== task_node(p
));
1211 static void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
1213 rq
->nr_numa_running
-= (p
->numa_preferred_nid
!= NUMA_NO_NODE
);
1214 rq
->nr_preferred_running
-= (p
->numa_preferred_nid
== task_node(p
));
1217 /* Shared or private faults. */
1218 #define NR_NUMA_HINT_FAULT_TYPES 2
1220 /* Memory and CPU locality */
1221 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1223 /* Averaged statistics, and temporary buffers. */
1224 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1226 pid_t
task_numa_group_id(struct task_struct
*p
)
1228 struct numa_group
*ng
;
1232 ng
= rcu_dereference(p
->numa_group
);
1241 * The averaged statistics, shared & private, memory & CPU,
1242 * occupy the first half of the array. The second half of the
1243 * array is for current counters, which are averaged into the
1244 * first set by task_numa_placement.
1246 static inline int task_faults_idx(enum numa_faults_stats s
, int nid
, int priv
)
1248 return NR_NUMA_HINT_FAULT_TYPES
* (s
* nr_node_ids
+ nid
) + priv
;
1251 static inline unsigned long task_faults(struct task_struct
*p
, int nid
)
1253 if (!p
->numa_faults
)
1256 return p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1257 p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1260 static inline unsigned long group_faults(struct task_struct
*p
, int nid
)
1262 struct numa_group
*ng
= deref_task_numa_group(p
);
1267 return ng
->faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1268 ng
->faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1271 static inline unsigned long group_faults_cpu(struct numa_group
*group
, int nid
)
1273 return group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1274 group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1277 static inline unsigned long group_faults_priv(struct numa_group
*ng
)
1279 unsigned long faults
= 0;
1282 for_each_online_node(node
) {
1283 faults
+= ng
->faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
1289 static inline unsigned long group_faults_shared(struct numa_group
*ng
)
1291 unsigned long faults
= 0;
1294 for_each_online_node(node
) {
1295 faults
+= ng
->faults
[task_faults_idx(NUMA_MEM
, node
, 0)];
1302 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1303 * considered part of a numa group's pseudo-interleaving set. Migrations
1304 * between these nodes are slowed down, to allow things to settle down.
1306 #define ACTIVE_NODE_FRACTION 3
1308 static bool numa_is_active_node(int nid
, struct numa_group
*ng
)
1310 return group_faults_cpu(ng
, nid
) * ACTIVE_NODE_FRACTION
> ng
->max_faults_cpu
;
1313 /* Handle placement on systems where not all nodes are directly connected. */
1314 static unsigned long score_nearby_nodes(struct task_struct
*p
, int nid
,
1315 int maxdist
, bool task
)
1317 unsigned long score
= 0;
1321 * All nodes are directly connected, and the same distance
1322 * from each other. No need for fancy placement algorithms.
1324 if (sched_numa_topology_type
== NUMA_DIRECT
)
1328 * This code is called for each node, introducing N^2 complexity,
1329 * which should be ok given the number of nodes rarely exceeds 8.
1331 for_each_online_node(node
) {
1332 unsigned long faults
;
1333 int dist
= node_distance(nid
, node
);
1336 * The furthest away nodes in the system are not interesting
1337 * for placement; nid was already counted.
1339 if (dist
== sched_max_numa_distance
|| node
== nid
)
1343 * On systems with a backplane NUMA topology, compare groups
1344 * of nodes, and move tasks towards the group with the most
1345 * memory accesses. When comparing two nodes at distance
1346 * "hoplimit", only nodes closer by than "hoplimit" are part
1347 * of each group. Skip other nodes.
1349 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1353 /* Add up the faults from nearby nodes. */
1355 faults
= task_faults(p
, node
);
1357 faults
= group_faults(p
, node
);
1360 * On systems with a glueless mesh NUMA topology, there are
1361 * no fixed "groups of nodes". Instead, nodes that are not
1362 * directly connected bounce traffic through intermediate
1363 * nodes; a numa_group can occupy any set of nodes.
1364 * The further away a node is, the less the faults count.
1365 * This seems to result in good task placement.
1367 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1368 faults
*= (sched_max_numa_distance
- dist
);
1369 faults
/= (sched_max_numa_distance
- LOCAL_DISTANCE
);
1379 * These return the fraction of accesses done by a particular task, or
1380 * task group, on a particular numa node. The group weight is given a
1381 * larger multiplier, in order to group tasks together that are almost
1382 * evenly spread out between numa nodes.
1384 static inline unsigned long task_weight(struct task_struct
*p
, int nid
,
1387 unsigned long faults
, total_faults
;
1389 if (!p
->numa_faults
)
1392 total_faults
= p
->total_numa_faults
;
1397 faults
= task_faults(p
, nid
);
1398 faults
+= score_nearby_nodes(p
, nid
, dist
, true);
1400 return 1000 * faults
/ total_faults
;
1403 static inline unsigned long group_weight(struct task_struct
*p
, int nid
,
1406 struct numa_group
*ng
= deref_task_numa_group(p
);
1407 unsigned long faults
, total_faults
;
1412 total_faults
= ng
->total_faults
;
1417 faults
= group_faults(p
, nid
);
1418 faults
+= score_nearby_nodes(p
, nid
, dist
, false);
1420 return 1000 * faults
/ total_faults
;
1423 bool should_numa_migrate_memory(struct task_struct
*p
, struct page
* page
,
1424 int src_nid
, int dst_cpu
)
1426 struct numa_group
*ng
= deref_curr_numa_group(p
);
1427 int dst_nid
= cpu_to_node(dst_cpu
);
1428 int last_cpupid
, this_cpupid
;
1430 this_cpupid
= cpu_pid_to_cpupid(dst_cpu
, current
->pid
);
1431 last_cpupid
= page_cpupid_xchg_last(page
, this_cpupid
);
1434 * Allow first faults or private faults to migrate immediately early in
1435 * the lifetime of a task. The magic number 4 is based on waiting for
1436 * two full passes of the "multi-stage node selection" test that is
1439 if ((p
->numa_preferred_nid
== NUMA_NO_NODE
|| p
->numa_scan_seq
<= 4) &&
1440 (cpupid_pid_unset(last_cpupid
) || cpupid_match_pid(p
, last_cpupid
)))
1444 * Multi-stage node selection is used in conjunction with a periodic
1445 * migration fault to build a temporal task<->page relation. By using
1446 * a two-stage filter we remove short/unlikely relations.
1448 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1449 * a task's usage of a particular page (n_p) per total usage of this
1450 * page (n_t) (in a given time-span) to a probability.
1452 * Our periodic faults will sample this probability and getting the
1453 * same result twice in a row, given these samples are fully
1454 * independent, is then given by P(n)^2, provided our sample period
1455 * is sufficiently short compared to the usage pattern.
1457 * This quadric squishes small probabilities, making it less likely we
1458 * act on an unlikely task<->page relation.
1460 if (!cpupid_pid_unset(last_cpupid
) &&
1461 cpupid_to_nid(last_cpupid
) != dst_nid
)
1464 /* Always allow migrate on private faults */
1465 if (cpupid_match_pid(p
, last_cpupid
))
1468 /* A shared fault, but p->numa_group has not been set up yet. */
1473 * Destination node is much more heavily used than the source
1474 * node? Allow migration.
1476 if (group_faults_cpu(ng
, dst_nid
) > group_faults_cpu(ng
, src_nid
) *
1477 ACTIVE_NODE_FRACTION
)
1481 * Distribute memory according to CPU & memory use on each node,
1482 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1484 * faults_cpu(dst) 3 faults_cpu(src)
1485 * --------------- * - > ---------------
1486 * faults_mem(dst) 4 faults_mem(src)
1488 return group_faults_cpu(ng
, dst_nid
) * group_faults(p
, src_nid
) * 3 >
1489 group_faults_cpu(ng
, src_nid
) * group_faults(p
, dst_nid
) * 4;
1493 * 'numa_type' describes the node at the moment of load balancing.
1496 /* The node has spare capacity that can be used to run more tasks. */
1499 * The node is fully used and the tasks don't compete for more CPU
1500 * cycles. Nevertheless, some tasks might wait before running.
1504 * The node is overloaded and can't provide expected CPU cycles to all
1510 /* Cached statistics for all CPUs within a node */
1513 unsigned long runnable
;
1515 /* Total compute capacity of CPUs on a node */
1516 unsigned long compute_capacity
;
1517 unsigned int nr_running
;
1518 unsigned int weight
;
1519 enum numa_type node_type
;
1523 static inline bool is_core_idle(int cpu
)
1525 #ifdef CONFIG_SCHED_SMT
1528 for_each_cpu(sibling
, cpu_smt_mask(cpu
)) {
1540 struct task_numa_env
{
1541 struct task_struct
*p
;
1543 int src_cpu
, src_nid
;
1544 int dst_cpu
, dst_nid
;
1546 struct numa_stats src_stats
, dst_stats
;
1551 struct task_struct
*best_task
;
1556 static unsigned long cpu_load(struct rq
*rq
);
1557 static unsigned long cpu_runnable(struct rq
*rq
);
1558 static unsigned long cpu_util(int cpu
);
1559 static inline long adjust_numa_imbalance(int imbalance
,
1560 int dst_running
, int dst_weight
);
1563 numa_type
numa_classify(unsigned int imbalance_pct
,
1564 struct numa_stats
*ns
)
1566 if ((ns
->nr_running
> ns
->weight
) &&
1567 (((ns
->compute_capacity
* 100) < (ns
->util
* imbalance_pct
)) ||
1568 ((ns
->compute_capacity
* imbalance_pct
) < (ns
->runnable
* 100))))
1569 return node_overloaded
;
1571 if ((ns
->nr_running
< ns
->weight
) ||
1572 (((ns
->compute_capacity
* 100) > (ns
->util
* imbalance_pct
)) &&
1573 ((ns
->compute_capacity
* imbalance_pct
) > (ns
->runnable
* 100))))
1574 return node_has_spare
;
1576 return node_fully_busy
;
1579 #ifdef CONFIG_SCHED_SMT
1580 /* Forward declarations of select_idle_sibling helpers */
1581 static inline bool test_idle_cores(int cpu
, bool def
);
1582 static inline int numa_idle_core(int idle_core
, int cpu
)
1584 if (!static_branch_likely(&sched_smt_present
) ||
1585 idle_core
>= 0 || !test_idle_cores(cpu
, false))
1589 * Prefer cores instead of packing HT siblings
1590 * and triggering future load balancing.
1592 if (is_core_idle(cpu
))
1598 static inline int numa_idle_core(int idle_core
, int cpu
)
1605 * Gather all necessary information to make NUMA balancing placement
1606 * decisions that are compatible with standard load balancer. This
1607 * borrows code and logic from update_sg_lb_stats but sharing a
1608 * common implementation is impractical.
1610 static void update_numa_stats(struct task_numa_env
*env
,
1611 struct numa_stats
*ns
, int nid
,
1614 int cpu
, idle_core
= -1;
1616 memset(ns
, 0, sizeof(*ns
));
1620 for_each_cpu(cpu
, cpumask_of_node(nid
)) {
1621 struct rq
*rq
= cpu_rq(cpu
);
1623 ns
->load
+= cpu_load(rq
);
1624 ns
->runnable
+= cpu_runnable(rq
);
1625 ns
->util
+= cpu_util(cpu
);
1626 ns
->nr_running
+= rq
->cfs
.h_nr_running
;
1627 ns
->compute_capacity
+= capacity_of(cpu
);
1629 if (find_idle
&& !rq
->nr_running
&& idle_cpu(cpu
)) {
1630 if (READ_ONCE(rq
->numa_migrate_on
) ||
1631 !cpumask_test_cpu(cpu
, env
->p
->cpus_ptr
))
1634 if (ns
->idle_cpu
== -1)
1637 idle_core
= numa_idle_core(idle_core
, cpu
);
1642 ns
->weight
= cpumask_weight(cpumask_of_node(nid
));
1644 ns
->node_type
= numa_classify(env
->imbalance_pct
, ns
);
1647 ns
->idle_cpu
= idle_core
;
1650 static void task_numa_assign(struct task_numa_env
*env
,
1651 struct task_struct
*p
, long imp
)
1653 struct rq
*rq
= cpu_rq(env
->dst_cpu
);
1655 /* Check if run-queue part of active NUMA balance. */
1656 if (env
->best_cpu
!= env
->dst_cpu
&& xchg(&rq
->numa_migrate_on
, 1)) {
1658 int start
= env
->dst_cpu
;
1660 /* Find alternative idle CPU. */
1661 for_each_cpu_wrap(cpu
, cpumask_of_node(env
->dst_nid
), start
) {
1662 if (cpu
== env
->best_cpu
|| !idle_cpu(cpu
) ||
1663 !cpumask_test_cpu(cpu
, env
->p
->cpus_ptr
)) {
1668 rq
= cpu_rq(env
->dst_cpu
);
1669 if (!xchg(&rq
->numa_migrate_on
, 1))
1673 /* Failed to find an alternative idle CPU */
1679 * Clear previous best_cpu/rq numa-migrate flag, since task now
1680 * found a better CPU to move/swap.
1682 if (env
->best_cpu
!= -1 && env
->best_cpu
!= env
->dst_cpu
) {
1683 rq
= cpu_rq(env
->best_cpu
);
1684 WRITE_ONCE(rq
->numa_migrate_on
, 0);
1688 put_task_struct(env
->best_task
);
1693 env
->best_imp
= imp
;
1694 env
->best_cpu
= env
->dst_cpu
;
1697 static bool load_too_imbalanced(long src_load
, long dst_load
,
1698 struct task_numa_env
*env
)
1701 long orig_src_load
, orig_dst_load
;
1702 long src_capacity
, dst_capacity
;
1705 * The load is corrected for the CPU capacity available on each node.
1708 * ------------ vs ---------
1709 * src_capacity dst_capacity
1711 src_capacity
= env
->src_stats
.compute_capacity
;
1712 dst_capacity
= env
->dst_stats
.compute_capacity
;
1714 imb
= abs(dst_load
* src_capacity
- src_load
* dst_capacity
);
1716 orig_src_load
= env
->src_stats
.load
;
1717 orig_dst_load
= env
->dst_stats
.load
;
1719 old_imb
= abs(orig_dst_load
* src_capacity
- orig_src_load
* dst_capacity
);
1721 /* Would this change make things worse? */
1722 return (imb
> old_imb
);
1726 * Maximum NUMA importance can be 1998 (2*999);
1727 * SMALLIMP @ 30 would be close to 1998/64.
1728 * Used to deter task migration.
1733 * This checks if the overall compute and NUMA accesses of the system would
1734 * be improved if the source tasks was migrated to the target dst_cpu taking
1735 * into account that it might be best if task running on the dst_cpu should
1736 * be exchanged with the source task
1738 static bool task_numa_compare(struct task_numa_env
*env
,
1739 long taskimp
, long groupimp
, bool maymove
)
1741 struct numa_group
*cur_ng
, *p_ng
= deref_curr_numa_group(env
->p
);
1742 struct rq
*dst_rq
= cpu_rq(env
->dst_cpu
);
1743 long imp
= p_ng
? groupimp
: taskimp
;
1744 struct task_struct
*cur
;
1745 long src_load
, dst_load
;
1746 int dist
= env
->dist
;
1749 bool stopsearch
= false;
1751 if (READ_ONCE(dst_rq
->numa_migrate_on
))
1755 cur
= rcu_dereference(dst_rq
->curr
);
1756 if (cur
&& ((cur
->flags
& PF_EXITING
) || is_idle_task(cur
)))
1760 * Because we have preemption enabled we can get migrated around and
1761 * end try selecting ourselves (current == env->p) as a swap candidate.
1763 if (cur
== env
->p
) {
1769 if (maymove
&& moveimp
>= env
->best_imp
)
1775 /* Skip this swap candidate if cannot move to the source cpu. */
1776 if (!cpumask_test_cpu(env
->src_cpu
, cur
->cpus_ptr
))
1780 * Skip this swap candidate if it is not moving to its preferred
1781 * node and the best task is.
1783 if (env
->best_task
&&
1784 env
->best_task
->numa_preferred_nid
== env
->src_nid
&&
1785 cur
->numa_preferred_nid
!= env
->src_nid
) {
1790 * "imp" is the fault differential for the source task between the
1791 * source and destination node. Calculate the total differential for
1792 * the source task and potential destination task. The more negative
1793 * the value is, the more remote accesses that would be expected to
1794 * be incurred if the tasks were swapped.
1796 * If dst and source tasks are in the same NUMA group, or not
1797 * in any group then look only at task weights.
1799 cur_ng
= rcu_dereference(cur
->numa_group
);
1800 if (cur_ng
== p_ng
) {
1801 imp
= taskimp
+ task_weight(cur
, env
->src_nid
, dist
) -
1802 task_weight(cur
, env
->dst_nid
, dist
);
1804 * Add some hysteresis to prevent swapping the
1805 * tasks within a group over tiny differences.
1811 * Compare the group weights. If a task is all by itself
1812 * (not part of a group), use the task weight instead.
1815 imp
+= group_weight(cur
, env
->src_nid
, dist
) -
1816 group_weight(cur
, env
->dst_nid
, dist
);
1818 imp
+= task_weight(cur
, env
->src_nid
, dist
) -
1819 task_weight(cur
, env
->dst_nid
, dist
);
1822 /* Discourage picking a task already on its preferred node */
1823 if (cur
->numa_preferred_nid
== env
->dst_nid
)
1827 * Encourage picking a task that moves to its preferred node.
1828 * This potentially makes imp larger than it's maximum of
1829 * 1998 (see SMALLIMP and task_weight for why) but in this
1830 * case, it does not matter.
1832 if (cur
->numa_preferred_nid
== env
->src_nid
)
1835 if (maymove
&& moveimp
> imp
&& moveimp
> env
->best_imp
) {
1842 * Prefer swapping with a task moving to its preferred node over a
1845 if (env
->best_task
&& cur
->numa_preferred_nid
== env
->src_nid
&&
1846 env
->best_task
->numa_preferred_nid
!= env
->src_nid
) {
1851 * If the NUMA importance is less than SMALLIMP,
1852 * task migration might only result in ping pong
1853 * of tasks and also hurt performance due to cache
1856 if (imp
< SMALLIMP
|| imp
<= env
->best_imp
+ SMALLIMP
/ 2)
1860 * In the overloaded case, try and keep the load balanced.
1862 load
= task_h_load(env
->p
) - task_h_load(cur
);
1866 dst_load
= env
->dst_stats
.load
+ load
;
1867 src_load
= env
->src_stats
.load
- load
;
1869 if (load_too_imbalanced(src_load
, dst_load
, env
))
1873 /* Evaluate an idle CPU for a task numa move. */
1875 int cpu
= env
->dst_stats
.idle_cpu
;
1877 /* Nothing cached so current CPU went idle since the search. */
1882 * If the CPU is no longer truly idle and the previous best CPU
1883 * is, keep using it.
1885 if (!idle_cpu(cpu
) && env
->best_cpu
>= 0 &&
1886 idle_cpu(env
->best_cpu
)) {
1887 cpu
= env
->best_cpu
;
1893 task_numa_assign(env
, cur
, imp
);
1896 * If a move to idle is allowed because there is capacity or load
1897 * balance improves then stop the search. While a better swap
1898 * candidate may exist, a search is not free.
1900 if (maymove
&& !cur
&& env
->best_cpu
>= 0 && idle_cpu(env
->best_cpu
))
1904 * If a swap candidate must be identified and the current best task
1905 * moves its preferred node then stop the search.
1907 if (!maymove
&& env
->best_task
&&
1908 env
->best_task
->numa_preferred_nid
== env
->src_nid
) {
1917 static void task_numa_find_cpu(struct task_numa_env
*env
,
1918 long taskimp
, long groupimp
)
1920 bool maymove
= false;
1924 * If dst node has spare capacity, then check if there is an
1925 * imbalance that would be overruled by the load balancer.
1927 if (env
->dst_stats
.node_type
== node_has_spare
) {
1928 unsigned int imbalance
;
1929 int src_running
, dst_running
;
1932 * Would movement cause an imbalance? Note that if src has
1933 * more running tasks that the imbalance is ignored as the
1934 * move improves the imbalance from the perspective of the
1935 * CPU load balancer.
1937 src_running
= env
->src_stats
.nr_running
- 1;
1938 dst_running
= env
->dst_stats
.nr_running
+ 1;
1939 imbalance
= max(0, dst_running
- src_running
);
1940 imbalance
= adjust_numa_imbalance(imbalance
, dst_running
,
1941 env
->dst_stats
.weight
);
1943 /* Use idle CPU if there is no imbalance */
1946 if (env
->dst_stats
.idle_cpu
>= 0) {
1947 env
->dst_cpu
= env
->dst_stats
.idle_cpu
;
1948 task_numa_assign(env
, NULL
, 0);
1953 long src_load
, dst_load
, load
;
1955 * If the improvement from just moving env->p direction is better
1956 * than swapping tasks around, check if a move is possible.
1958 load
= task_h_load(env
->p
);
1959 dst_load
= env
->dst_stats
.load
+ load
;
1960 src_load
= env
->src_stats
.load
- load
;
1961 maymove
= !load_too_imbalanced(src_load
, dst_load
, env
);
1964 for_each_cpu(cpu
, cpumask_of_node(env
->dst_nid
)) {
1965 /* Skip this CPU if the source task cannot migrate */
1966 if (!cpumask_test_cpu(cpu
, env
->p
->cpus_ptr
))
1970 if (task_numa_compare(env
, taskimp
, groupimp
, maymove
))
1975 static int task_numa_migrate(struct task_struct
*p
)
1977 struct task_numa_env env
= {
1980 .src_cpu
= task_cpu(p
),
1981 .src_nid
= task_node(p
),
1983 .imbalance_pct
= 112,
1989 unsigned long taskweight
, groupweight
;
1990 struct sched_domain
*sd
;
1991 long taskimp
, groupimp
;
1992 struct numa_group
*ng
;
1997 * Pick the lowest SD_NUMA domain, as that would have the smallest
1998 * imbalance and would be the first to start moving tasks about.
2000 * And we want to avoid any moving of tasks about, as that would create
2001 * random movement of tasks -- counter the numa conditions we're trying
2005 sd
= rcu_dereference(per_cpu(sd_numa
, env
.src_cpu
));
2007 env
.imbalance_pct
= 100 + (sd
->imbalance_pct
- 100) / 2;
2011 * Cpusets can break the scheduler domain tree into smaller
2012 * balance domains, some of which do not cross NUMA boundaries.
2013 * Tasks that are "trapped" in such domains cannot be migrated
2014 * elsewhere, so there is no point in (re)trying.
2016 if (unlikely(!sd
)) {
2017 sched_setnuma(p
, task_node(p
));
2021 env
.dst_nid
= p
->numa_preferred_nid
;
2022 dist
= env
.dist
= node_distance(env
.src_nid
, env
.dst_nid
);
2023 taskweight
= task_weight(p
, env
.src_nid
, dist
);
2024 groupweight
= group_weight(p
, env
.src_nid
, dist
);
2025 update_numa_stats(&env
, &env
.src_stats
, env
.src_nid
, false);
2026 taskimp
= task_weight(p
, env
.dst_nid
, dist
) - taskweight
;
2027 groupimp
= group_weight(p
, env
.dst_nid
, dist
) - groupweight
;
2028 update_numa_stats(&env
, &env
.dst_stats
, env
.dst_nid
, true);
2030 /* Try to find a spot on the preferred nid. */
2031 task_numa_find_cpu(&env
, taskimp
, groupimp
);
2034 * Look at other nodes in these cases:
2035 * - there is no space available on the preferred_nid
2036 * - the task is part of a numa_group that is interleaved across
2037 * multiple NUMA nodes; in order to better consolidate the group,
2038 * we need to check other locations.
2040 ng
= deref_curr_numa_group(p
);
2041 if (env
.best_cpu
== -1 || (ng
&& ng
->active_nodes
> 1)) {
2042 for_each_online_node(nid
) {
2043 if (nid
== env
.src_nid
|| nid
== p
->numa_preferred_nid
)
2046 dist
= node_distance(env
.src_nid
, env
.dst_nid
);
2047 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
2049 taskweight
= task_weight(p
, env
.src_nid
, dist
);
2050 groupweight
= group_weight(p
, env
.src_nid
, dist
);
2053 /* Only consider nodes where both task and groups benefit */
2054 taskimp
= task_weight(p
, nid
, dist
) - taskweight
;
2055 groupimp
= group_weight(p
, nid
, dist
) - groupweight
;
2056 if (taskimp
< 0 && groupimp
< 0)
2061 update_numa_stats(&env
, &env
.dst_stats
, env
.dst_nid
, true);
2062 task_numa_find_cpu(&env
, taskimp
, groupimp
);
2067 * If the task is part of a workload that spans multiple NUMA nodes,
2068 * and is migrating into one of the workload's active nodes, remember
2069 * this node as the task's preferred numa node, so the workload can
2071 * A task that migrated to a second choice node will be better off
2072 * trying for a better one later. Do not set the preferred node here.
2075 if (env
.best_cpu
== -1)
2078 nid
= cpu_to_node(env
.best_cpu
);
2080 if (nid
!= p
->numa_preferred_nid
)
2081 sched_setnuma(p
, nid
);
2084 /* No better CPU than the current one was found. */
2085 if (env
.best_cpu
== -1) {
2086 trace_sched_stick_numa(p
, env
.src_cpu
, NULL
, -1);
2090 best_rq
= cpu_rq(env
.best_cpu
);
2091 if (env
.best_task
== NULL
) {
2092 ret
= migrate_task_to(p
, env
.best_cpu
);
2093 WRITE_ONCE(best_rq
->numa_migrate_on
, 0);
2095 trace_sched_stick_numa(p
, env
.src_cpu
, NULL
, env
.best_cpu
);
2099 ret
= migrate_swap(p
, env
.best_task
, env
.best_cpu
, env
.src_cpu
);
2100 WRITE_ONCE(best_rq
->numa_migrate_on
, 0);
2103 trace_sched_stick_numa(p
, env
.src_cpu
, env
.best_task
, env
.best_cpu
);
2104 put_task_struct(env
.best_task
);
2108 /* Attempt to migrate a task to a CPU on the preferred node. */
2109 static void numa_migrate_preferred(struct task_struct
*p
)
2111 unsigned long interval
= HZ
;
2113 /* This task has no NUMA fault statistics yet */
2114 if (unlikely(p
->numa_preferred_nid
== NUMA_NO_NODE
|| !p
->numa_faults
))
2117 /* Periodically retry migrating the task to the preferred node */
2118 interval
= min(interval
, msecs_to_jiffies(p
->numa_scan_period
) / 16);
2119 p
->numa_migrate_retry
= jiffies
+ interval
;
2121 /* Success if task is already running on preferred CPU */
2122 if (task_node(p
) == p
->numa_preferred_nid
)
2125 /* Otherwise, try migrate to a CPU on the preferred node */
2126 task_numa_migrate(p
);
2130 * Find out how many nodes on the workload is actively running on. Do this by
2131 * tracking the nodes from which NUMA hinting faults are triggered. This can
2132 * be different from the set of nodes where the workload's memory is currently
2135 static void numa_group_count_active_nodes(struct numa_group
*numa_group
)
2137 unsigned long faults
, max_faults
= 0;
2138 int nid
, active_nodes
= 0;
2140 for_each_online_node(nid
) {
2141 faults
= group_faults_cpu(numa_group
, nid
);
2142 if (faults
> max_faults
)
2143 max_faults
= faults
;
2146 for_each_online_node(nid
) {
2147 faults
= group_faults_cpu(numa_group
, nid
);
2148 if (faults
* ACTIVE_NODE_FRACTION
> max_faults
)
2152 numa_group
->max_faults_cpu
= max_faults
;
2153 numa_group
->active_nodes
= active_nodes
;
2157 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
2158 * increments. The more local the fault statistics are, the higher the scan
2159 * period will be for the next scan window. If local/(local+remote) ratio is
2160 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
2161 * the scan period will decrease. Aim for 70% local accesses.
2163 #define NUMA_PERIOD_SLOTS 10
2164 #define NUMA_PERIOD_THRESHOLD 7
2167 * Increase the scan period (slow down scanning) if the majority of
2168 * our memory is already on our local node, or if the majority of
2169 * the page accesses are shared with other processes.
2170 * Otherwise, decrease the scan period.
2172 static void update_task_scan_period(struct task_struct
*p
,
2173 unsigned long shared
, unsigned long private)
2175 unsigned int period_slot
;
2176 int lr_ratio
, ps_ratio
;
2179 unsigned long remote
= p
->numa_faults_locality
[0];
2180 unsigned long local
= p
->numa_faults_locality
[1];
2183 * If there were no record hinting faults then either the task is
2184 * completely idle or all activity is areas that are not of interest
2185 * to automatic numa balancing. Related to that, if there were failed
2186 * migration then it implies we are migrating too quickly or the local
2187 * node is overloaded. In either case, scan slower
2189 if (local
+ shared
== 0 || p
->numa_faults_locality
[2]) {
2190 p
->numa_scan_period
= min(p
->numa_scan_period_max
,
2191 p
->numa_scan_period
<< 1);
2193 p
->mm
->numa_next_scan
= jiffies
+
2194 msecs_to_jiffies(p
->numa_scan_period
);
2200 * Prepare to scale scan period relative to the current period.
2201 * == NUMA_PERIOD_THRESHOLD scan period stays the same
2202 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
2203 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
2205 period_slot
= DIV_ROUND_UP(p
->numa_scan_period
, NUMA_PERIOD_SLOTS
);
2206 lr_ratio
= (local
* NUMA_PERIOD_SLOTS
) / (local
+ remote
);
2207 ps_ratio
= (private * NUMA_PERIOD_SLOTS
) / (private + shared
);
2209 if (ps_ratio
>= NUMA_PERIOD_THRESHOLD
) {
2211 * Most memory accesses are local. There is no need to
2212 * do fast NUMA scanning, since memory is already local.
2214 int slot
= ps_ratio
- NUMA_PERIOD_THRESHOLD
;
2217 diff
= slot
* period_slot
;
2218 } else if (lr_ratio
>= NUMA_PERIOD_THRESHOLD
) {
2220 * Most memory accesses are shared with other tasks.
2221 * There is no point in continuing fast NUMA scanning,
2222 * since other tasks may just move the memory elsewhere.
2224 int slot
= lr_ratio
- NUMA_PERIOD_THRESHOLD
;
2227 diff
= slot
* period_slot
;
2230 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
2231 * yet they are not on the local NUMA node. Speed up
2232 * NUMA scanning to get the memory moved over.
2234 int ratio
= max(lr_ratio
, ps_ratio
);
2235 diff
= -(NUMA_PERIOD_THRESHOLD
- ratio
) * period_slot
;
2238 p
->numa_scan_period
= clamp(p
->numa_scan_period
+ diff
,
2239 task_scan_min(p
), task_scan_max(p
));
2240 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
2244 * Get the fraction of time the task has been running since the last
2245 * NUMA placement cycle. The scheduler keeps similar statistics, but
2246 * decays those on a 32ms period, which is orders of magnitude off
2247 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
2248 * stats only if the task is so new there are no NUMA statistics yet.
2250 static u64
numa_get_avg_runtime(struct task_struct
*p
, u64
*period
)
2252 u64 runtime
, delta
, now
;
2253 /* Use the start of this time slice to avoid calculations. */
2254 now
= p
->se
.exec_start
;
2255 runtime
= p
->se
.sum_exec_runtime
;
2257 if (p
->last_task_numa_placement
) {
2258 delta
= runtime
- p
->last_sum_exec_runtime
;
2259 *period
= now
- p
->last_task_numa_placement
;
2261 /* Avoid time going backwards, prevent potential divide error: */
2262 if (unlikely((s64
)*period
< 0))
2265 delta
= p
->se
.avg
.load_sum
;
2266 *period
= LOAD_AVG_MAX
;
2269 p
->last_sum_exec_runtime
= runtime
;
2270 p
->last_task_numa_placement
= now
;
2276 * Determine the preferred nid for a task in a numa_group. This needs to
2277 * be done in a way that produces consistent results with group_weight,
2278 * otherwise workloads might not converge.
2280 static int preferred_group_nid(struct task_struct
*p
, int nid
)
2285 /* Direct connections between all NUMA nodes. */
2286 if (sched_numa_topology_type
== NUMA_DIRECT
)
2290 * On a system with glueless mesh NUMA topology, group_weight
2291 * scores nodes according to the number of NUMA hinting faults on
2292 * both the node itself, and on nearby nodes.
2294 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
2295 unsigned long score
, max_score
= 0;
2296 int node
, max_node
= nid
;
2298 dist
= sched_max_numa_distance
;
2300 for_each_online_node(node
) {
2301 score
= group_weight(p
, node
, dist
);
2302 if (score
> max_score
) {
2311 * Finding the preferred nid in a system with NUMA backplane
2312 * interconnect topology is more involved. The goal is to locate
2313 * tasks from numa_groups near each other in the system, and
2314 * untangle workloads from different sides of the system. This requires
2315 * searching down the hierarchy of node groups, recursively searching
2316 * inside the highest scoring group of nodes. The nodemask tricks
2317 * keep the complexity of the search down.
2319 nodes
= node_online_map
;
2320 for (dist
= sched_max_numa_distance
; dist
> LOCAL_DISTANCE
; dist
--) {
2321 unsigned long max_faults
= 0;
2322 nodemask_t max_group
= NODE_MASK_NONE
;
2325 /* Are there nodes at this distance from each other? */
2326 if (!find_numa_distance(dist
))
2329 for_each_node_mask(a
, nodes
) {
2330 unsigned long faults
= 0;
2331 nodemask_t this_group
;
2332 nodes_clear(this_group
);
2334 /* Sum group's NUMA faults; includes a==b case. */
2335 for_each_node_mask(b
, nodes
) {
2336 if (node_distance(a
, b
) < dist
) {
2337 faults
+= group_faults(p
, b
);
2338 node_set(b
, this_group
);
2339 node_clear(b
, nodes
);
2343 /* Remember the top group. */
2344 if (faults
> max_faults
) {
2345 max_faults
= faults
;
2346 max_group
= this_group
;
2348 * subtle: at the smallest distance there is
2349 * just one node left in each "group", the
2350 * winner is the preferred nid.
2355 /* Next round, evaluate the nodes within max_group. */
2363 static void task_numa_placement(struct task_struct
*p
)
2365 int seq
, nid
, max_nid
= NUMA_NO_NODE
;
2366 unsigned long max_faults
= 0;
2367 unsigned long fault_types
[2] = { 0, 0 };
2368 unsigned long total_faults
;
2369 u64 runtime
, period
;
2370 spinlock_t
*group_lock
= NULL
;
2371 struct numa_group
*ng
;
2374 * The p->mm->numa_scan_seq field gets updated without
2375 * exclusive access. Use READ_ONCE() here to ensure
2376 * that the field is read in a single access:
2378 seq
= READ_ONCE(p
->mm
->numa_scan_seq
);
2379 if (p
->numa_scan_seq
== seq
)
2381 p
->numa_scan_seq
= seq
;
2382 p
->numa_scan_period_max
= task_scan_max(p
);
2384 total_faults
= p
->numa_faults_locality
[0] +
2385 p
->numa_faults_locality
[1];
2386 runtime
= numa_get_avg_runtime(p
, &period
);
2388 /* If the task is part of a group prevent parallel updates to group stats */
2389 ng
= deref_curr_numa_group(p
);
2391 group_lock
= &ng
->lock
;
2392 spin_lock_irq(group_lock
);
2395 /* Find the node with the highest number of faults */
2396 for_each_online_node(nid
) {
2397 /* Keep track of the offsets in numa_faults array */
2398 int mem_idx
, membuf_idx
, cpu_idx
, cpubuf_idx
;
2399 unsigned long faults
= 0, group_faults
= 0;
2402 for (priv
= 0; priv
< NR_NUMA_HINT_FAULT_TYPES
; priv
++) {
2403 long diff
, f_diff
, f_weight
;
2405 mem_idx
= task_faults_idx(NUMA_MEM
, nid
, priv
);
2406 membuf_idx
= task_faults_idx(NUMA_MEMBUF
, nid
, priv
);
2407 cpu_idx
= task_faults_idx(NUMA_CPU
, nid
, priv
);
2408 cpubuf_idx
= task_faults_idx(NUMA_CPUBUF
, nid
, priv
);
2410 /* Decay existing window, copy faults since last scan */
2411 diff
= p
->numa_faults
[membuf_idx
] - p
->numa_faults
[mem_idx
] / 2;
2412 fault_types
[priv
] += p
->numa_faults
[membuf_idx
];
2413 p
->numa_faults
[membuf_idx
] = 0;
2416 * Normalize the faults_from, so all tasks in a group
2417 * count according to CPU use, instead of by the raw
2418 * number of faults. Tasks with little runtime have
2419 * little over-all impact on throughput, and thus their
2420 * faults are less important.
2422 f_weight
= div64_u64(runtime
<< 16, period
+ 1);
2423 f_weight
= (f_weight
* p
->numa_faults
[cpubuf_idx
]) /
2425 f_diff
= f_weight
- p
->numa_faults
[cpu_idx
] / 2;
2426 p
->numa_faults
[cpubuf_idx
] = 0;
2428 p
->numa_faults
[mem_idx
] += diff
;
2429 p
->numa_faults
[cpu_idx
] += f_diff
;
2430 faults
+= p
->numa_faults
[mem_idx
];
2431 p
->total_numa_faults
+= diff
;
2434 * safe because we can only change our own group
2436 * mem_idx represents the offset for a given
2437 * nid and priv in a specific region because it
2438 * is at the beginning of the numa_faults array.
2440 ng
->faults
[mem_idx
] += diff
;
2441 ng
->faults_cpu
[mem_idx
] += f_diff
;
2442 ng
->total_faults
+= diff
;
2443 group_faults
+= ng
->faults
[mem_idx
];
2448 if (faults
> max_faults
) {
2449 max_faults
= faults
;
2452 } else if (group_faults
> max_faults
) {
2453 max_faults
= group_faults
;
2459 numa_group_count_active_nodes(ng
);
2460 spin_unlock_irq(group_lock
);
2461 max_nid
= preferred_group_nid(p
, max_nid
);
2465 /* Set the new preferred node */
2466 if (max_nid
!= p
->numa_preferred_nid
)
2467 sched_setnuma(p
, max_nid
);
2470 update_task_scan_period(p
, fault_types
[0], fault_types
[1]);
2473 static inline int get_numa_group(struct numa_group
*grp
)
2475 return refcount_inc_not_zero(&grp
->refcount
);
2478 static inline void put_numa_group(struct numa_group
*grp
)
2480 if (refcount_dec_and_test(&grp
->refcount
))
2481 kfree_rcu(grp
, rcu
);
2484 static void task_numa_group(struct task_struct
*p
, int cpupid
, int flags
,
2487 struct numa_group
*grp
, *my_grp
;
2488 struct task_struct
*tsk
;
2490 int cpu
= cpupid_to_cpu(cpupid
);
2493 if (unlikely(!deref_curr_numa_group(p
))) {
2494 unsigned int size
= sizeof(struct numa_group
) +
2495 4*nr_node_ids
*sizeof(unsigned long);
2497 grp
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
2501 refcount_set(&grp
->refcount
, 1);
2502 grp
->active_nodes
= 1;
2503 grp
->max_faults_cpu
= 0;
2504 spin_lock_init(&grp
->lock
);
2506 /* Second half of the array tracks nids where faults happen */
2507 grp
->faults_cpu
= grp
->faults
+ NR_NUMA_HINT_FAULT_TYPES
*
2510 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2511 grp
->faults
[i
] = p
->numa_faults
[i
];
2513 grp
->total_faults
= p
->total_numa_faults
;
2516 rcu_assign_pointer(p
->numa_group
, grp
);
2520 tsk
= READ_ONCE(cpu_rq(cpu
)->curr
);
2522 if (!cpupid_match_pid(tsk
, cpupid
))
2525 grp
= rcu_dereference(tsk
->numa_group
);
2529 my_grp
= deref_curr_numa_group(p
);
2534 * Only join the other group if its bigger; if we're the bigger group,
2535 * the other task will join us.
2537 if (my_grp
->nr_tasks
> grp
->nr_tasks
)
2541 * Tie-break on the grp address.
2543 if (my_grp
->nr_tasks
== grp
->nr_tasks
&& my_grp
> grp
)
2546 /* Always join threads in the same process. */
2547 if (tsk
->mm
== current
->mm
)
2550 /* Simple filter to avoid false positives due to PID collisions */
2551 if (flags
& TNF_SHARED
)
2554 /* Update priv based on whether false sharing was detected */
2557 if (join
&& !get_numa_group(grp
))
2565 BUG_ON(irqs_disabled());
2566 double_lock_irq(&my_grp
->lock
, &grp
->lock
);
2568 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++) {
2569 my_grp
->faults
[i
] -= p
->numa_faults
[i
];
2570 grp
->faults
[i
] += p
->numa_faults
[i
];
2572 my_grp
->total_faults
-= p
->total_numa_faults
;
2573 grp
->total_faults
+= p
->total_numa_faults
;
2578 spin_unlock(&my_grp
->lock
);
2579 spin_unlock_irq(&grp
->lock
);
2581 rcu_assign_pointer(p
->numa_group
, grp
);
2583 put_numa_group(my_grp
);
2592 * Get rid of NUMA statistics associated with a task (either current or dead).
2593 * If @final is set, the task is dead and has reached refcount zero, so we can
2594 * safely free all relevant data structures. Otherwise, there might be
2595 * concurrent reads from places like load balancing and procfs, and we should
2596 * reset the data back to default state without freeing ->numa_faults.
2598 void task_numa_free(struct task_struct
*p
, bool final
)
2600 /* safe: p either is current or is being freed by current */
2601 struct numa_group
*grp
= rcu_dereference_raw(p
->numa_group
);
2602 unsigned long *numa_faults
= p
->numa_faults
;
2603 unsigned long flags
;
2610 spin_lock_irqsave(&grp
->lock
, flags
);
2611 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2612 grp
->faults
[i
] -= p
->numa_faults
[i
];
2613 grp
->total_faults
-= p
->total_numa_faults
;
2616 spin_unlock_irqrestore(&grp
->lock
, flags
);
2617 RCU_INIT_POINTER(p
->numa_group
, NULL
);
2618 put_numa_group(grp
);
2622 p
->numa_faults
= NULL
;
2625 p
->total_numa_faults
= 0;
2626 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2632 * Got a PROT_NONE fault for a page on @node.
2634 void task_numa_fault(int last_cpupid
, int mem_node
, int pages
, int flags
)
2636 struct task_struct
*p
= current
;
2637 bool migrated
= flags
& TNF_MIGRATED
;
2638 int cpu_node
= task_node(current
);
2639 int local
= !!(flags
& TNF_FAULT_LOCAL
);
2640 struct numa_group
*ng
;
2643 if (!static_branch_likely(&sched_numa_balancing
))
2646 /* for example, ksmd faulting in a user's mm */
2650 /* Allocate buffer to track faults on a per-node basis */
2651 if (unlikely(!p
->numa_faults
)) {
2652 int size
= sizeof(*p
->numa_faults
) *
2653 NR_NUMA_HINT_FAULT_BUCKETS
* nr_node_ids
;
2655 p
->numa_faults
= kzalloc(size
, GFP_KERNEL
|__GFP_NOWARN
);
2656 if (!p
->numa_faults
)
2659 p
->total_numa_faults
= 0;
2660 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
2664 * First accesses are treated as private, otherwise consider accesses
2665 * to be private if the accessing pid has not changed
2667 if (unlikely(last_cpupid
== (-1 & LAST_CPUPID_MASK
))) {
2670 priv
= cpupid_match_pid(p
, last_cpupid
);
2671 if (!priv
&& !(flags
& TNF_NO_GROUP
))
2672 task_numa_group(p
, last_cpupid
, flags
, &priv
);
2676 * If a workload spans multiple NUMA nodes, a shared fault that
2677 * occurs wholly within the set of nodes that the workload is
2678 * actively using should be counted as local. This allows the
2679 * scan rate to slow down when a workload has settled down.
2681 ng
= deref_curr_numa_group(p
);
2682 if (!priv
&& !local
&& ng
&& ng
->active_nodes
> 1 &&
2683 numa_is_active_node(cpu_node
, ng
) &&
2684 numa_is_active_node(mem_node
, ng
))
2688 * Retry to migrate task to preferred node periodically, in case it
2689 * previously failed, or the scheduler moved us.
2691 if (time_after(jiffies
, p
->numa_migrate_retry
)) {
2692 task_numa_placement(p
);
2693 numa_migrate_preferred(p
);
2697 p
->numa_pages_migrated
+= pages
;
2698 if (flags
& TNF_MIGRATE_FAIL
)
2699 p
->numa_faults_locality
[2] += pages
;
2701 p
->numa_faults
[task_faults_idx(NUMA_MEMBUF
, mem_node
, priv
)] += pages
;
2702 p
->numa_faults
[task_faults_idx(NUMA_CPUBUF
, cpu_node
, priv
)] += pages
;
2703 p
->numa_faults_locality
[local
] += pages
;
2706 static void reset_ptenuma_scan(struct task_struct
*p
)
2709 * We only did a read acquisition of the mmap sem, so
2710 * p->mm->numa_scan_seq is written to without exclusive access
2711 * and the update is not guaranteed to be atomic. That's not
2712 * much of an issue though, since this is just used for
2713 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2714 * expensive, to avoid any form of compiler optimizations:
2716 WRITE_ONCE(p
->mm
->numa_scan_seq
, READ_ONCE(p
->mm
->numa_scan_seq
) + 1);
2717 p
->mm
->numa_scan_offset
= 0;
2721 * The expensive part of numa migration is done from task_work context.
2722 * Triggered from task_tick_numa().
2724 static void task_numa_work(struct callback_head
*work
)
2726 unsigned long migrate
, next_scan
, now
= jiffies
;
2727 struct task_struct
*p
= current
;
2728 struct mm_struct
*mm
= p
->mm
;
2729 u64 runtime
= p
->se
.sum_exec_runtime
;
2730 struct vm_area_struct
*vma
;
2731 unsigned long start
, end
;
2732 unsigned long nr_pte_updates
= 0;
2733 long pages
, virtpages
;
2735 SCHED_WARN_ON(p
!= container_of(work
, struct task_struct
, numa_work
));
2739 * Who cares about NUMA placement when they're dying.
2741 * NOTE: make sure not to dereference p->mm before this check,
2742 * exit_task_work() happens _after_ exit_mm() so we could be called
2743 * without p->mm even though we still had it when we enqueued this
2746 if (p
->flags
& PF_EXITING
)
2749 if (!mm
->numa_next_scan
) {
2750 mm
->numa_next_scan
= now
+
2751 msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
2755 * Enforce maximal scan/migration frequency..
2757 migrate
= mm
->numa_next_scan
;
2758 if (time_before(now
, migrate
))
2761 if (p
->numa_scan_period
== 0) {
2762 p
->numa_scan_period_max
= task_scan_max(p
);
2763 p
->numa_scan_period
= task_scan_start(p
);
2766 next_scan
= now
+ msecs_to_jiffies(p
->numa_scan_period
);
2767 if (cmpxchg(&mm
->numa_next_scan
, migrate
, next_scan
) != migrate
)
2771 * Delay this task enough that another task of this mm will likely win
2772 * the next time around.
2774 p
->node_stamp
+= 2 * TICK_NSEC
;
2776 start
= mm
->numa_scan_offset
;
2777 pages
= sysctl_numa_balancing_scan_size
;
2778 pages
<<= 20 - PAGE_SHIFT
; /* MB in pages */
2779 virtpages
= pages
* 8; /* Scan up to this much virtual space */
2784 if (!mmap_read_trylock(mm
))
2786 vma
= find_vma(mm
, start
);
2788 reset_ptenuma_scan(p
);
2792 for (; vma
; vma
= vma
->vm_next
) {
2793 if (!vma_migratable(vma
) || !vma_policy_mof(vma
) ||
2794 is_vm_hugetlb_page(vma
) || (vma
->vm_flags
& VM_MIXEDMAP
)) {
2799 * Shared library pages mapped by multiple processes are not
2800 * migrated as it is expected they are cache replicated. Avoid
2801 * hinting faults in read-only file-backed mappings or the vdso
2802 * as migrating the pages will be of marginal benefit.
2805 (vma
->vm_file
&& (vma
->vm_flags
& (VM_READ
|VM_WRITE
)) == (VM_READ
)))
2809 * Skip inaccessible VMAs to avoid any confusion between
2810 * PROT_NONE and NUMA hinting ptes
2812 if (!vma_is_accessible(vma
))
2816 start
= max(start
, vma
->vm_start
);
2817 end
= ALIGN(start
+ (pages
<< PAGE_SHIFT
), HPAGE_SIZE
);
2818 end
= min(end
, vma
->vm_end
);
2819 nr_pte_updates
= change_prot_numa(vma
, start
, end
);
2822 * Try to scan sysctl_numa_balancing_size worth of
2823 * hpages that have at least one present PTE that
2824 * is not already pte-numa. If the VMA contains
2825 * areas that are unused or already full of prot_numa
2826 * PTEs, scan up to virtpages, to skip through those
2830 pages
-= (end
- start
) >> PAGE_SHIFT
;
2831 virtpages
-= (end
- start
) >> PAGE_SHIFT
;
2834 if (pages
<= 0 || virtpages
<= 0)
2838 } while (end
!= vma
->vm_end
);
2843 * It is possible to reach the end of the VMA list but the last few
2844 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2845 * would find the !migratable VMA on the next scan but not reset the
2846 * scanner to the start so check it now.
2849 mm
->numa_scan_offset
= start
;
2851 reset_ptenuma_scan(p
);
2852 mmap_read_unlock(mm
);
2855 * Make sure tasks use at least 32x as much time to run other code
2856 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2857 * Usually update_task_scan_period slows down scanning enough; on an
2858 * overloaded system we need to limit overhead on a per task basis.
2860 if (unlikely(p
->se
.sum_exec_runtime
!= runtime
)) {
2861 u64 diff
= p
->se
.sum_exec_runtime
- runtime
;
2862 p
->node_stamp
+= 32 * diff
;
2866 void init_numa_balancing(unsigned long clone_flags
, struct task_struct
*p
)
2869 struct mm_struct
*mm
= p
->mm
;
2872 mm_users
= atomic_read(&mm
->mm_users
);
2873 if (mm_users
== 1) {
2874 mm
->numa_next_scan
= jiffies
+ msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
2875 mm
->numa_scan_seq
= 0;
2879 p
->numa_scan_seq
= mm
? mm
->numa_scan_seq
: 0;
2880 p
->numa_scan_period
= sysctl_numa_balancing_scan_delay
;
2881 /* Protect against double add, see task_tick_numa and task_numa_work */
2882 p
->numa_work
.next
= &p
->numa_work
;
2883 p
->numa_faults
= NULL
;
2884 RCU_INIT_POINTER(p
->numa_group
, NULL
);
2885 p
->last_task_numa_placement
= 0;
2886 p
->last_sum_exec_runtime
= 0;
2888 init_task_work(&p
->numa_work
, task_numa_work
);
2890 /* New address space, reset the preferred nid */
2891 if (!(clone_flags
& CLONE_VM
)) {
2892 p
->numa_preferred_nid
= NUMA_NO_NODE
;
2897 * New thread, keep existing numa_preferred_nid which should be copied
2898 * already by arch_dup_task_struct but stagger when scans start.
2903 delay
= min_t(unsigned int, task_scan_max(current
),
2904 current
->numa_scan_period
* mm_users
* NSEC_PER_MSEC
);
2905 delay
+= 2 * TICK_NSEC
;
2906 p
->node_stamp
= delay
;
2911 * Drive the periodic memory faults..
2913 static void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2915 struct callback_head
*work
= &curr
->numa_work
;
2919 * We don't care about NUMA placement if we don't have memory.
2921 if ((curr
->flags
& (PF_EXITING
| PF_KTHREAD
)) || work
->next
!= work
)
2925 * Using runtime rather than walltime has the dual advantage that
2926 * we (mostly) drive the selection from busy threads and that the
2927 * task needs to have done some actual work before we bother with
2930 now
= curr
->se
.sum_exec_runtime
;
2931 period
= (u64
)curr
->numa_scan_period
* NSEC_PER_MSEC
;
2933 if (now
> curr
->node_stamp
+ period
) {
2934 if (!curr
->node_stamp
)
2935 curr
->numa_scan_period
= task_scan_start(curr
);
2936 curr
->node_stamp
+= period
;
2938 if (!time_before(jiffies
, curr
->mm
->numa_next_scan
))
2939 task_work_add(curr
, work
, TWA_RESUME
);
2943 static void update_scan_period(struct task_struct
*p
, int new_cpu
)
2945 int src_nid
= cpu_to_node(task_cpu(p
));
2946 int dst_nid
= cpu_to_node(new_cpu
);
2948 if (!static_branch_likely(&sched_numa_balancing
))
2951 if (!p
->mm
|| !p
->numa_faults
|| (p
->flags
& PF_EXITING
))
2954 if (src_nid
== dst_nid
)
2958 * Allow resets if faults have been trapped before one scan
2959 * has completed. This is most likely due to a new task that
2960 * is pulled cross-node due to wakeups or load balancing.
2962 if (p
->numa_scan_seq
) {
2964 * Avoid scan adjustments if moving to the preferred
2965 * node or if the task was not previously running on
2966 * the preferred node.
2968 if (dst_nid
== p
->numa_preferred_nid
||
2969 (p
->numa_preferred_nid
!= NUMA_NO_NODE
&&
2970 src_nid
!= p
->numa_preferred_nid
))
2974 p
->numa_scan_period
= task_scan_start(p
);
2978 static void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2982 static inline void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
2986 static inline void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
2990 static inline void update_scan_period(struct task_struct
*p
, int new_cpu
)
2994 #endif /* CONFIG_NUMA_BALANCING */
2997 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2999 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
3001 if (entity_is_task(se
)) {
3002 struct rq
*rq
= rq_of(cfs_rq
);
3004 account_numa_enqueue(rq
, task_of(se
));
3005 list_add(&se
->group_node
, &rq
->cfs_tasks
);
3008 cfs_rq
->nr_running
++;
3012 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3014 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
3016 if (entity_is_task(se
)) {
3017 account_numa_dequeue(rq_of(cfs_rq
), task_of(se
));
3018 list_del_init(&se
->group_node
);
3021 cfs_rq
->nr_running
--;
3025 * Signed add and clamp on underflow.
3027 * Explicitly do a load-store to ensure the intermediate value never hits
3028 * memory. This allows lockless observations without ever seeing the negative
3031 #define add_positive(_ptr, _val) do { \
3032 typeof(_ptr) ptr = (_ptr); \
3033 typeof(_val) val = (_val); \
3034 typeof(*ptr) res, var = READ_ONCE(*ptr); \
3038 if (val < 0 && res > var) \
3041 WRITE_ONCE(*ptr, res); \
3045 * Unsigned subtract and clamp on underflow.
3047 * Explicitly do a load-store to ensure the intermediate value never hits
3048 * memory. This allows lockless observations without ever seeing the negative
3051 #define sub_positive(_ptr, _val) do { \
3052 typeof(_ptr) ptr = (_ptr); \
3053 typeof(*ptr) val = (_val); \
3054 typeof(*ptr) res, var = READ_ONCE(*ptr); \
3058 WRITE_ONCE(*ptr, res); \
3062 * Remove and clamp on negative, from a local variable.
3064 * A variant of sub_positive(), which does not use explicit load-store
3065 * and is thus optimized for local variable updates.
3067 #define lsub_positive(_ptr, _val) do { \
3068 typeof(_ptr) ptr = (_ptr); \
3069 *ptr -= min_t(typeof(*ptr), *ptr, _val); \
3074 enqueue_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3076 cfs_rq
->avg
.load_avg
+= se
->avg
.load_avg
;
3077 cfs_rq
->avg
.load_sum
+= se_weight(se
) * se
->avg
.load_sum
;
3081 dequeue_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3083 sub_positive(&cfs_rq
->avg
.load_avg
, se
->avg
.load_avg
);
3084 sub_positive(&cfs_rq
->avg
.load_sum
, se_weight(se
) * se
->avg
.load_sum
);
3088 enqueue_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) { }
3090 dequeue_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) { }
3093 static void reweight_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
3094 unsigned long weight
)
3097 /* commit outstanding execution time */
3098 if (cfs_rq
->curr
== se
)
3099 update_curr(cfs_rq
);
3100 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
3102 dequeue_load_avg(cfs_rq
, se
);
3104 update_load_set(&se
->load
, weight
);
3108 u32 divider
= get_pelt_divider(&se
->avg
);
3110 se
->avg
.load_avg
= div_u64(se_weight(se
) * se
->avg
.load_sum
, divider
);
3114 enqueue_load_avg(cfs_rq
, se
);
3116 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
3120 void reweight_task(struct task_struct
*p
, int prio
)
3122 struct sched_entity
*se
= &p
->se
;
3123 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3124 struct load_weight
*load
= &se
->load
;
3125 unsigned long weight
= scale_load(sched_prio_to_weight
[prio
]);
3127 reweight_entity(cfs_rq
, se
, weight
);
3128 load
->inv_weight
= sched_prio_to_wmult
[prio
];
3131 #ifdef CONFIG_FAIR_GROUP_SCHED
3134 * All this does is approximate the hierarchical proportion which includes that
3135 * global sum we all love to hate.
3137 * That is, the weight of a group entity, is the proportional share of the
3138 * group weight based on the group runqueue weights. That is:
3140 * tg->weight * grq->load.weight
3141 * ge->load.weight = ----------------------------- (1)
3142 * \Sum grq->load.weight
3144 * Now, because computing that sum is prohibitively expensive to compute (been
3145 * there, done that) we approximate it with this average stuff. The average
3146 * moves slower and therefore the approximation is cheaper and more stable.
3148 * So instead of the above, we substitute:
3150 * grq->load.weight -> grq->avg.load_avg (2)
3152 * which yields the following:
3154 * tg->weight * grq->avg.load_avg
3155 * ge->load.weight = ------------------------------ (3)
3158 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
3160 * That is shares_avg, and it is right (given the approximation (2)).
3162 * The problem with it is that because the average is slow -- it was designed
3163 * to be exactly that of course -- this leads to transients in boundary
3164 * conditions. In specific, the case where the group was idle and we start the
3165 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
3166 * yielding bad latency etc..
3168 * Now, in that special case (1) reduces to:
3170 * tg->weight * grq->load.weight
3171 * ge->load.weight = ----------------------------- = tg->weight (4)
3174 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
3176 * So what we do is modify our approximation (3) to approach (4) in the (near)
3181 * tg->weight * grq->load.weight
3182 * --------------------------------------------------- (5)
3183 * tg->load_avg - grq->avg.load_avg + grq->load.weight
3185 * But because grq->load.weight can drop to 0, resulting in a divide by zero,
3186 * we need to use grq->avg.load_avg as its lower bound, which then gives:
3189 * tg->weight * grq->load.weight
3190 * ge->load.weight = ----------------------------- (6)
3195 * tg_load_avg' = tg->load_avg - grq->avg.load_avg +
3196 * max(grq->load.weight, grq->avg.load_avg)
3198 * And that is shares_weight and is icky. In the (near) UP case it approaches
3199 * (4) while in the normal case it approaches (3). It consistently
3200 * overestimates the ge->load.weight and therefore:
3202 * \Sum ge->load.weight >= tg->weight
3206 static long calc_group_shares(struct cfs_rq
*cfs_rq
)
3208 long tg_weight
, tg_shares
, load
, shares
;
3209 struct task_group
*tg
= cfs_rq
->tg
;
3211 tg_shares
= READ_ONCE(tg
->shares
);
3213 load
= max(scale_load_down(cfs_rq
->load
.weight
), cfs_rq
->avg
.load_avg
);
3215 tg_weight
= atomic_long_read(&tg
->load_avg
);
3217 /* Ensure tg_weight >= load */
3218 tg_weight
-= cfs_rq
->tg_load_avg_contrib
;
3221 shares
= (tg_shares
* load
);
3223 shares
/= tg_weight
;
3226 * MIN_SHARES has to be unscaled here to support per-CPU partitioning
3227 * of a group with small tg->shares value. It is a floor value which is
3228 * assigned as a minimum load.weight to the sched_entity representing
3229 * the group on a CPU.
3231 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
3232 * on an 8-core system with 8 tasks each runnable on one CPU shares has
3233 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
3234 * case no task is runnable on a CPU MIN_SHARES=2 should be returned
3237 return clamp_t(long, shares
, MIN_SHARES
, tg_shares
);
3239 #endif /* CONFIG_SMP */
3241 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
);
3244 * Recomputes the group entity based on the current state of its group
3247 static void update_cfs_group(struct sched_entity
*se
)
3249 struct cfs_rq
*gcfs_rq
= group_cfs_rq(se
);
3255 if (throttled_hierarchy(gcfs_rq
))
3259 shares
= READ_ONCE(gcfs_rq
->tg
->shares
);
3261 if (likely(se
->load
.weight
== shares
))
3264 shares
= calc_group_shares(gcfs_rq
);
3267 reweight_entity(cfs_rq_of(se
), se
, shares
);
3270 #else /* CONFIG_FAIR_GROUP_SCHED */
3271 static inline void update_cfs_group(struct sched_entity
*se
)
3274 #endif /* CONFIG_FAIR_GROUP_SCHED */
3276 static inline void cfs_rq_util_change(struct cfs_rq
*cfs_rq
, int flags
)
3278 struct rq
*rq
= rq_of(cfs_rq
);
3280 if (&rq
->cfs
== cfs_rq
) {
3282 * There are a few boundary cases this might miss but it should
3283 * get called often enough that that should (hopefully) not be
3286 * It will not get called when we go idle, because the idle
3287 * thread is a different class (!fair), nor will the utilization
3288 * number include things like RT tasks.
3290 * As is, the util number is not freq-invariant (we'd have to
3291 * implement arch_scale_freq_capacity() for that).
3295 cpufreq_update_util(rq
, flags
);
3300 #ifdef CONFIG_FAIR_GROUP_SCHED
3302 * update_tg_load_avg - update the tg's load avg
3303 * @cfs_rq: the cfs_rq whose avg changed
3305 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
3306 * However, because tg->load_avg is a global value there are performance
3309 * In order to avoid having to look at the other cfs_rq's, we use a
3310 * differential update where we store the last value we propagated. This in
3311 * turn allows skipping updates if the differential is 'small'.
3313 * Updating tg's load_avg is necessary before update_cfs_share().
3315 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
)
3317 long delta
= cfs_rq
->avg
.load_avg
- cfs_rq
->tg_load_avg_contrib
;
3320 * No need to update load_avg for root_task_group as it is not used.
3322 if (cfs_rq
->tg
== &root_task_group
)
3325 if (abs(delta
) > cfs_rq
->tg_load_avg_contrib
/ 64) {
3326 atomic_long_add(delta
, &cfs_rq
->tg
->load_avg
);
3327 cfs_rq
->tg_load_avg_contrib
= cfs_rq
->avg
.load_avg
;
3332 * Called within set_task_rq() right before setting a task's CPU. The
3333 * caller only guarantees p->pi_lock is held; no other assumptions,
3334 * including the state of rq->lock, should be made.
3336 void set_task_rq_fair(struct sched_entity
*se
,
3337 struct cfs_rq
*prev
, struct cfs_rq
*next
)
3339 u64 p_last_update_time
;
3340 u64 n_last_update_time
;
3342 if (!sched_feat(ATTACH_AGE_LOAD
))
3346 * We are supposed to update the task to "current" time, then its up to
3347 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
3348 * getting what current time is, so simply throw away the out-of-date
3349 * time. This will result in the wakee task is less decayed, but giving
3350 * the wakee more load sounds not bad.
3352 if (!(se
->avg
.last_update_time
&& prev
))
3355 #ifndef CONFIG_64BIT
3357 u64 p_last_update_time_copy
;
3358 u64 n_last_update_time_copy
;
3361 p_last_update_time_copy
= prev
->load_last_update_time_copy
;
3362 n_last_update_time_copy
= next
->load_last_update_time_copy
;
3366 p_last_update_time
= prev
->avg
.last_update_time
;
3367 n_last_update_time
= next
->avg
.last_update_time
;
3369 } while (p_last_update_time
!= p_last_update_time_copy
||
3370 n_last_update_time
!= n_last_update_time_copy
);
3373 p_last_update_time
= prev
->avg
.last_update_time
;
3374 n_last_update_time
= next
->avg
.last_update_time
;
3376 __update_load_avg_blocked_se(p_last_update_time
, se
);
3377 se
->avg
.last_update_time
= n_last_update_time
;
3382 * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
3383 * propagate its contribution. The key to this propagation is the invariant
3384 * that for each group:
3386 * ge->avg == grq->avg (1)
3388 * _IFF_ we look at the pure running and runnable sums. Because they
3389 * represent the very same entity, just at different points in the hierarchy.
3391 * Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial
3392 * and simply copies the running/runnable sum over (but still wrong, because
3393 * the group entity and group rq do not have their PELT windows aligned).
3395 * However, update_tg_cfs_load() is more complex. So we have:
3397 * ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2)
3399 * And since, like util, the runnable part should be directly transferable,
3400 * the following would _appear_ to be the straight forward approach:
3402 * grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3)
3404 * And per (1) we have:
3406 * ge->avg.runnable_avg == grq->avg.runnable_avg
3410 * ge->load.weight * grq->avg.load_avg
3411 * ge->avg.load_avg = ----------------------------------- (4)
3414 * Except that is wrong!
3416 * Because while for entities historical weight is not important and we
3417 * really only care about our future and therefore can consider a pure
3418 * runnable sum, runqueues can NOT do this.
3420 * We specifically want runqueues to have a load_avg that includes
3421 * historical weights. Those represent the blocked load, the load we expect
3422 * to (shortly) return to us. This only works by keeping the weights as
3423 * integral part of the sum. We therefore cannot decompose as per (3).
3425 * Another reason this doesn't work is that runnable isn't a 0-sum entity.
3426 * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
3427 * rq itself is runnable anywhere between 2/3 and 1 depending on how the
3428 * runnable section of these tasks overlap (or not). If they were to perfectly
3429 * align the rq as a whole would be runnable 2/3 of the time. If however we
3430 * always have at least 1 runnable task, the rq as a whole is always runnable.
3432 * So we'll have to approximate.. :/
3434 * Given the constraint:
3436 * ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3438 * We can construct a rule that adds runnable to a rq by assuming minimal
3441 * On removal, we'll assume each task is equally runnable; which yields:
3443 * grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3445 * XXX: only do this for the part of runnable > running ?
3450 update_tg_cfs_util(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, struct cfs_rq
*gcfs_rq
)
3452 long delta
= gcfs_rq
->avg
.util_avg
- se
->avg
.util_avg
;
3455 /* Nothing to update */
3460 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3461 * See ___update_load_avg() for details.
3463 divider
= get_pelt_divider(&cfs_rq
->avg
);
3465 /* Set new sched_entity's utilization */
3466 se
->avg
.util_avg
= gcfs_rq
->avg
.util_avg
;
3467 se
->avg
.util_sum
= se
->avg
.util_avg
* divider
;
3469 /* Update parent cfs_rq utilization */
3470 add_positive(&cfs_rq
->avg
.util_avg
, delta
);
3471 cfs_rq
->avg
.util_sum
= cfs_rq
->avg
.util_avg
* divider
;
3475 update_tg_cfs_runnable(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, struct cfs_rq
*gcfs_rq
)
3477 long delta
= gcfs_rq
->avg
.runnable_avg
- se
->avg
.runnable_avg
;
3480 /* Nothing to update */
3485 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3486 * See ___update_load_avg() for details.
3488 divider
= get_pelt_divider(&cfs_rq
->avg
);
3490 /* Set new sched_entity's runnable */
3491 se
->avg
.runnable_avg
= gcfs_rq
->avg
.runnable_avg
;
3492 se
->avg
.runnable_sum
= se
->avg
.runnable_avg
* divider
;
3494 /* Update parent cfs_rq runnable */
3495 add_positive(&cfs_rq
->avg
.runnable_avg
, delta
);
3496 cfs_rq
->avg
.runnable_sum
= cfs_rq
->avg
.runnable_avg
* divider
;
3500 update_tg_cfs_load(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, struct cfs_rq
*gcfs_rq
)
3502 long delta_avg
, running_sum
, runnable_sum
= gcfs_rq
->prop_runnable_sum
;
3503 unsigned long load_avg
;
3511 gcfs_rq
->prop_runnable_sum
= 0;
3514 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3515 * See ___update_load_avg() for details.
3517 divider
= get_pelt_divider(&cfs_rq
->avg
);
3519 if (runnable_sum
>= 0) {
3521 * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
3522 * the CPU is saturated running == runnable.
3524 runnable_sum
+= se
->avg
.load_sum
;
3525 runnable_sum
= min_t(long, runnable_sum
, divider
);
3528 * Estimate the new unweighted runnable_sum of the gcfs_rq by
3529 * assuming all tasks are equally runnable.
3531 if (scale_load_down(gcfs_rq
->load
.weight
)) {
3532 load_sum
= div_s64(gcfs_rq
->avg
.load_sum
,
3533 scale_load_down(gcfs_rq
->load
.weight
));
3536 /* But make sure to not inflate se's runnable */
3537 runnable_sum
= min(se
->avg
.load_sum
, load_sum
);
3541 * runnable_sum can't be lower than running_sum
3542 * Rescale running sum to be in the same range as runnable sum
3543 * running_sum is in [0 : LOAD_AVG_MAX << SCHED_CAPACITY_SHIFT]
3544 * runnable_sum is in [0 : LOAD_AVG_MAX]
3546 running_sum
= se
->avg
.util_sum
>> SCHED_CAPACITY_SHIFT
;
3547 runnable_sum
= max(runnable_sum
, running_sum
);
3549 load_sum
= (s64
)se_weight(se
) * runnable_sum
;
3550 load_avg
= div_s64(load_sum
, divider
);
3552 delta_sum
= load_sum
- (s64
)se_weight(se
) * se
->avg
.load_sum
;
3553 delta_avg
= load_avg
- se
->avg
.load_avg
;
3555 se
->avg
.load_sum
= runnable_sum
;
3556 se
->avg
.load_avg
= load_avg
;
3557 add_positive(&cfs_rq
->avg
.load_avg
, delta_avg
);
3558 add_positive(&cfs_rq
->avg
.load_sum
, delta_sum
);
3561 static inline void add_tg_cfs_propagate(struct cfs_rq
*cfs_rq
, long runnable_sum
)
3563 cfs_rq
->propagate
= 1;
3564 cfs_rq
->prop_runnable_sum
+= runnable_sum
;
3567 /* Update task and its cfs_rq load average */
3568 static inline int propagate_entity_load_avg(struct sched_entity
*se
)
3570 struct cfs_rq
*cfs_rq
, *gcfs_rq
;
3572 if (entity_is_task(se
))
3575 gcfs_rq
= group_cfs_rq(se
);
3576 if (!gcfs_rq
->propagate
)
3579 gcfs_rq
->propagate
= 0;
3581 cfs_rq
= cfs_rq_of(se
);
3583 add_tg_cfs_propagate(cfs_rq
, gcfs_rq
->prop_runnable_sum
);
3585 update_tg_cfs_util(cfs_rq
, se
, gcfs_rq
);
3586 update_tg_cfs_runnable(cfs_rq
, se
, gcfs_rq
);
3587 update_tg_cfs_load(cfs_rq
, se
, gcfs_rq
);
3589 trace_pelt_cfs_tp(cfs_rq
);
3590 trace_pelt_se_tp(se
);
3596 * Check if we need to update the load and the utilization of a blocked
3599 static inline bool skip_blocked_update(struct sched_entity
*se
)
3601 struct cfs_rq
*gcfs_rq
= group_cfs_rq(se
);
3604 * If sched_entity still have not zero load or utilization, we have to
3607 if (se
->avg
.load_avg
|| se
->avg
.util_avg
)
3611 * If there is a pending propagation, we have to update the load and
3612 * the utilization of the sched_entity:
3614 if (gcfs_rq
->propagate
)
3618 * Otherwise, the load and the utilization of the sched_entity is
3619 * already zero and there is no pending propagation, so it will be a
3620 * waste of time to try to decay it:
3625 #else /* CONFIG_FAIR_GROUP_SCHED */
3627 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
) {}
3629 static inline int propagate_entity_load_avg(struct sched_entity
*se
)
3634 static inline void add_tg_cfs_propagate(struct cfs_rq
*cfs_rq
, long runnable_sum
) {}
3636 #endif /* CONFIG_FAIR_GROUP_SCHED */
3639 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
3640 * @now: current time, as per cfs_rq_clock_pelt()
3641 * @cfs_rq: cfs_rq to update
3643 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
3644 * avg. The immediate corollary is that all (fair) tasks must be attached, see
3645 * post_init_entity_util_avg().
3647 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
3649 * Returns true if the load decayed or we removed load.
3651 * Since both these conditions indicate a changed cfs_rq->avg.load we should
3652 * call update_tg_load_avg() when this function returns true.
3655 update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
)
3657 unsigned long removed_load
= 0, removed_util
= 0, removed_runnable
= 0;
3658 struct sched_avg
*sa
= &cfs_rq
->avg
;
3661 if (cfs_rq
->removed
.nr
) {
3663 u32 divider
= get_pelt_divider(&cfs_rq
->avg
);
3665 raw_spin_lock(&cfs_rq
->removed
.lock
);
3666 swap(cfs_rq
->removed
.util_avg
, removed_util
);
3667 swap(cfs_rq
->removed
.load_avg
, removed_load
);
3668 swap(cfs_rq
->removed
.runnable_avg
, removed_runnable
);
3669 cfs_rq
->removed
.nr
= 0;
3670 raw_spin_unlock(&cfs_rq
->removed
.lock
);
3673 sub_positive(&sa
->load_avg
, r
);
3674 sub_positive(&sa
->load_sum
, r
* divider
);
3677 sub_positive(&sa
->util_avg
, r
);
3678 sub_positive(&sa
->util_sum
, r
* divider
);
3680 r
= removed_runnable
;
3681 sub_positive(&sa
->runnable_avg
, r
);
3682 sub_positive(&sa
->runnable_sum
, r
* divider
);
3685 * removed_runnable is the unweighted version of removed_load so we
3686 * can use it to estimate removed_load_sum.
3688 add_tg_cfs_propagate(cfs_rq
,
3689 -(long)(removed_runnable
* divider
) >> SCHED_CAPACITY_SHIFT
);
3694 decayed
|= __update_load_avg_cfs_rq(now
, cfs_rq
);
3696 #ifndef CONFIG_64BIT
3698 cfs_rq
->load_last_update_time_copy
= sa
->last_update_time
;
3705 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
3706 * @cfs_rq: cfs_rq to attach to
3707 * @se: sched_entity to attach
3709 * Must call update_cfs_rq_load_avg() before this, since we rely on
3710 * cfs_rq->avg.last_update_time being current.
3712 static void attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3715 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3716 * See ___update_load_avg() for details.
3718 u32 divider
= get_pelt_divider(&cfs_rq
->avg
);
3721 * When we attach the @se to the @cfs_rq, we must align the decay
3722 * window because without that, really weird and wonderful things can
3727 se
->avg
.last_update_time
= cfs_rq
->avg
.last_update_time
;
3728 se
->avg
.period_contrib
= cfs_rq
->avg
.period_contrib
;
3731 * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
3732 * period_contrib. This isn't strictly correct, but since we're
3733 * entirely outside of the PELT hierarchy, nobody cares if we truncate
3736 se
->avg
.util_sum
= se
->avg
.util_avg
* divider
;
3738 se
->avg
.runnable_sum
= se
->avg
.runnable_avg
* divider
;
3740 se
->avg
.load_sum
= divider
;
3741 if (se_weight(se
)) {
3743 div_u64(se
->avg
.load_avg
* se
->avg
.load_sum
, se_weight(se
));
3746 enqueue_load_avg(cfs_rq
, se
);
3747 cfs_rq
->avg
.util_avg
+= se
->avg
.util_avg
;
3748 cfs_rq
->avg
.util_sum
+= se
->avg
.util_sum
;
3749 cfs_rq
->avg
.runnable_avg
+= se
->avg
.runnable_avg
;
3750 cfs_rq
->avg
.runnable_sum
+= se
->avg
.runnable_sum
;
3752 add_tg_cfs_propagate(cfs_rq
, se
->avg
.load_sum
);
3754 cfs_rq_util_change(cfs_rq
, 0);
3756 trace_pelt_cfs_tp(cfs_rq
);
3760 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
3761 * @cfs_rq: cfs_rq to detach from
3762 * @se: sched_entity to detach
3764 * Must call update_cfs_rq_load_avg() before this, since we rely on
3765 * cfs_rq->avg.last_update_time being current.
3767 static void detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3769 dequeue_load_avg(cfs_rq
, se
);
3770 sub_positive(&cfs_rq
->avg
.util_avg
, se
->avg
.util_avg
);
3771 sub_positive(&cfs_rq
->avg
.util_sum
, se
->avg
.util_sum
);
3772 sub_positive(&cfs_rq
->avg
.runnable_avg
, se
->avg
.runnable_avg
);
3773 sub_positive(&cfs_rq
->avg
.runnable_sum
, se
->avg
.runnable_sum
);
3775 add_tg_cfs_propagate(cfs_rq
, -se
->avg
.load_sum
);
3777 cfs_rq_util_change(cfs_rq
, 0);
3779 trace_pelt_cfs_tp(cfs_rq
);
3783 * Optional action to be done while updating the load average
3785 #define UPDATE_TG 0x1
3786 #define SKIP_AGE_LOAD 0x2
3787 #define DO_ATTACH 0x4
3789 /* Update task and its cfs_rq load average */
3790 static inline void update_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3792 u64 now
= cfs_rq_clock_pelt(cfs_rq
);
3796 * Track task load average for carrying it to new CPU after migrated, and
3797 * track group sched_entity load average for task_h_load calc in migration
3799 if (se
->avg
.last_update_time
&& !(flags
& SKIP_AGE_LOAD
))
3800 __update_load_avg_se(now
, cfs_rq
, se
);
3802 decayed
= update_cfs_rq_load_avg(now
, cfs_rq
);
3803 decayed
|= propagate_entity_load_avg(se
);
3805 if (!se
->avg
.last_update_time
&& (flags
& DO_ATTACH
)) {
3808 * DO_ATTACH means we're here from enqueue_entity().
3809 * !last_update_time means we've passed through
3810 * migrate_task_rq_fair() indicating we migrated.
3812 * IOW we're enqueueing a task on a new CPU.
3814 attach_entity_load_avg(cfs_rq
, se
);
3815 update_tg_load_avg(cfs_rq
);
3817 } else if (decayed
) {
3818 cfs_rq_util_change(cfs_rq
, 0);
3820 if (flags
& UPDATE_TG
)
3821 update_tg_load_avg(cfs_rq
);
3825 #ifndef CONFIG_64BIT
3826 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3828 u64 last_update_time_copy
;
3829 u64 last_update_time
;
3832 last_update_time_copy
= cfs_rq
->load_last_update_time_copy
;
3834 last_update_time
= cfs_rq
->avg
.last_update_time
;
3835 } while (last_update_time
!= last_update_time_copy
);
3837 return last_update_time
;
3840 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3842 return cfs_rq
->avg
.last_update_time
;
3847 * Synchronize entity load avg of dequeued entity without locking
3850 static void sync_entity_load_avg(struct sched_entity
*se
)
3852 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3853 u64 last_update_time
;
3855 last_update_time
= cfs_rq_last_update_time(cfs_rq
);
3856 __update_load_avg_blocked_se(last_update_time
, se
);
3860 * Task first catches up with cfs_rq, and then subtract
3861 * itself from the cfs_rq (task must be off the queue now).
3863 static void remove_entity_load_avg(struct sched_entity
*se
)
3865 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3866 unsigned long flags
;
3869 * tasks cannot exit without having gone through wake_up_new_task() ->
3870 * post_init_entity_util_avg() which will have added things to the
3871 * cfs_rq, so we can remove unconditionally.
3874 sync_entity_load_avg(se
);
3876 raw_spin_lock_irqsave(&cfs_rq
->removed
.lock
, flags
);
3877 ++cfs_rq
->removed
.nr
;
3878 cfs_rq
->removed
.util_avg
+= se
->avg
.util_avg
;
3879 cfs_rq
->removed
.load_avg
+= se
->avg
.load_avg
;
3880 cfs_rq
->removed
.runnable_avg
+= se
->avg
.runnable_avg
;
3881 raw_spin_unlock_irqrestore(&cfs_rq
->removed
.lock
, flags
);
3884 static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq
*cfs_rq
)
3886 return cfs_rq
->avg
.runnable_avg
;
3889 static inline unsigned long cfs_rq_load_avg(struct cfs_rq
*cfs_rq
)
3891 return cfs_rq
->avg
.load_avg
;
3894 static int newidle_balance(struct rq
*this_rq
, struct rq_flags
*rf
);
3896 static inline unsigned long task_util(struct task_struct
*p
)
3898 return READ_ONCE(p
->se
.avg
.util_avg
);
3901 static inline unsigned long _task_util_est(struct task_struct
*p
)
3903 struct util_est ue
= READ_ONCE(p
->se
.avg
.util_est
);
3905 return (max(ue
.ewma
, ue
.enqueued
) | UTIL_AVG_UNCHANGED
);
3908 static inline unsigned long task_util_est(struct task_struct
*p
)
3910 return max(task_util(p
), _task_util_est(p
));
3913 #ifdef CONFIG_UCLAMP_TASK
3914 static inline unsigned long uclamp_task_util(struct task_struct
*p
)
3916 return clamp(task_util_est(p
),
3917 uclamp_eff_value(p
, UCLAMP_MIN
),
3918 uclamp_eff_value(p
, UCLAMP_MAX
));
3921 static inline unsigned long uclamp_task_util(struct task_struct
*p
)
3923 return task_util_est(p
);
3927 static inline void util_est_enqueue(struct cfs_rq
*cfs_rq
,
3928 struct task_struct
*p
)
3930 unsigned int enqueued
;
3932 if (!sched_feat(UTIL_EST
))
3935 /* Update root cfs_rq's estimated utilization */
3936 enqueued
= cfs_rq
->avg
.util_est
.enqueued
;
3937 enqueued
+= _task_util_est(p
);
3938 WRITE_ONCE(cfs_rq
->avg
.util_est
.enqueued
, enqueued
);
3940 trace_sched_util_est_cfs_tp(cfs_rq
);
3943 static inline void util_est_dequeue(struct cfs_rq
*cfs_rq
,
3944 struct task_struct
*p
)
3946 unsigned int enqueued
;
3948 if (!sched_feat(UTIL_EST
))
3951 /* Update root cfs_rq's estimated utilization */
3952 enqueued
= cfs_rq
->avg
.util_est
.enqueued
;
3953 enqueued
-= min_t(unsigned int, enqueued
, _task_util_est(p
));
3954 WRITE_ONCE(cfs_rq
->avg
.util_est
.enqueued
, enqueued
);
3956 trace_sched_util_est_cfs_tp(cfs_rq
);
3959 #define UTIL_EST_MARGIN (SCHED_CAPACITY_SCALE / 100)
3962 * Check if a (signed) value is within a specified (unsigned) margin,
3963 * based on the observation that:
3965 * abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
3967 * NOTE: this only works when value + margin < INT_MAX.
3969 static inline bool within_margin(int value
, int margin
)
3971 return ((unsigned int)(value
+ margin
- 1) < (2 * margin
- 1));
3974 static inline void util_est_update(struct cfs_rq
*cfs_rq
,
3975 struct task_struct
*p
,
3978 long last_ewma_diff
, last_enqueued_diff
;
3981 if (!sched_feat(UTIL_EST
))
3985 * Skip update of task's estimated utilization when the task has not
3986 * yet completed an activation, e.g. being migrated.
3992 * If the PELT values haven't changed since enqueue time,
3993 * skip the util_est update.
3995 ue
= p
->se
.avg
.util_est
;
3996 if (ue
.enqueued
& UTIL_AVG_UNCHANGED
)
3999 last_enqueued_diff
= ue
.enqueued
;
4002 * Reset EWMA on utilization increases, the moving average is used only
4003 * to smooth utilization decreases.
4005 ue
.enqueued
= (task_util(p
) | UTIL_AVG_UNCHANGED
);
4006 if (sched_feat(UTIL_EST_FASTUP
)) {
4007 if (ue
.ewma
< ue
.enqueued
) {
4008 ue
.ewma
= ue
.enqueued
;
4014 * Skip update of task's estimated utilization when its members are
4015 * already ~1% close to its last activation value.
4017 last_ewma_diff
= ue
.enqueued
- ue
.ewma
;
4018 last_enqueued_diff
-= ue
.enqueued
;
4019 if (within_margin(last_ewma_diff
, UTIL_EST_MARGIN
)) {
4020 if (!within_margin(last_enqueued_diff
, UTIL_EST_MARGIN
))
4027 * To avoid overestimation of actual task utilization, skip updates if
4028 * we cannot grant there is idle time in this CPU.
4030 if (task_util(p
) > capacity_orig_of(cpu_of(rq_of(cfs_rq
))))
4034 * Update Task's estimated utilization
4036 * When *p completes an activation we can consolidate another sample
4037 * of the task size. This is done by storing the current PELT value
4038 * as ue.enqueued and by using this value to update the Exponential
4039 * Weighted Moving Average (EWMA):
4041 * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1)
4042 * = w * task_util(p) + ewma(t-1) - w * ewma(t-1)
4043 * = w * (task_util(p) - ewma(t-1)) + ewma(t-1)
4044 * = w * ( last_ewma_diff ) + ewma(t-1)
4045 * = w * (last_ewma_diff + ewma(t-1) / w)
4047 * Where 'w' is the weight of new samples, which is configured to be
4048 * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
4050 ue
.ewma
<<= UTIL_EST_WEIGHT_SHIFT
;
4051 ue
.ewma
+= last_ewma_diff
;
4052 ue
.ewma
>>= UTIL_EST_WEIGHT_SHIFT
;
4054 WRITE_ONCE(p
->se
.avg
.util_est
, ue
);
4056 trace_sched_util_est_se_tp(&p
->se
);
4059 static inline int task_fits_capacity(struct task_struct
*p
, long capacity
)
4061 return fits_capacity(uclamp_task_util(p
), capacity
);
4064 static inline void update_misfit_status(struct task_struct
*p
, struct rq
*rq
)
4066 if (!static_branch_unlikely(&sched_asym_cpucapacity
))
4069 if (!p
|| p
->nr_cpus_allowed
== 1) {
4070 rq
->misfit_task_load
= 0;
4074 if (task_fits_capacity(p
, capacity_of(cpu_of(rq
)))) {
4075 rq
->misfit_task_load
= 0;
4080 * Make sure that misfit_task_load will not be null even if
4081 * task_h_load() returns 0.
4083 rq
->misfit_task_load
= max_t(unsigned long, task_h_load(p
), 1);
4086 #else /* CONFIG_SMP */
4088 #define UPDATE_TG 0x0
4089 #define SKIP_AGE_LOAD 0x0
4090 #define DO_ATTACH 0x0
4092 static inline void update_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int not_used1
)
4094 cfs_rq_util_change(cfs_rq
, 0);
4097 static inline void remove_entity_load_avg(struct sched_entity
*se
) {}
4100 attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
4102 detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
4104 static inline int newidle_balance(struct rq
*rq
, struct rq_flags
*rf
)
4110 util_est_enqueue(struct cfs_rq
*cfs_rq
, struct task_struct
*p
) {}
4113 util_est_dequeue(struct cfs_rq
*cfs_rq
, struct task_struct
*p
) {}
4116 util_est_update(struct cfs_rq
*cfs_rq
, struct task_struct
*p
,
4118 static inline void update_misfit_status(struct task_struct
*p
, struct rq
*rq
) {}
4120 #endif /* CONFIG_SMP */
4122 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
4124 #ifdef CONFIG_SCHED_DEBUG
4125 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
4130 if (d
> 3*sysctl_sched_latency
)
4131 schedstat_inc(cfs_rq
->nr_spread_over
);
4136 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
4138 u64 vruntime
= cfs_rq
->min_vruntime
;
4141 * The 'current' period is already promised to the current tasks,
4142 * however the extra weight of the new task will slow them down a
4143 * little, place the new task so that it fits in the slot that
4144 * stays open at the end.
4146 if (initial
&& sched_feat(START_DEBIT
))
4147 vruntime
+= sched_vslice(cfs_rq
, se
);
4149 /* sleeps up to a single latency don't count. */
4151 unsigned long thresh
= sysctl_sched_latency
;
4154 * Halve their sleep time's effect, to allow
4155 * for a gentler effect of sleepers:
4157 if (sched_feat(GENTLE_FAIR_SLEEPERS
))
4163 /* ensure we never gain time by being placed backwards. */
4164 se
->vruntime
= max_vruntime(se
->vruntime
, vruntime
);
4167 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
);
4169 static inline void check_schedstat_required(void)
4171 #ifdef CONFIG_SCHEDSTATS
4172 if (schedstat_enabled())
4175 /* Force schedstat enabled if a dependent tracepoint is active */
4176 if (trace_sched_stat_wait_enabled() ||
4177 trace_sched_stat_sleep_enabled() ||
4178 trace_sched_stat_iowait_enabled() ||
4179 trace_sched_stat_blocked_enabled() ||
4180 trace_sched_stat_runtime_enabled()) {
4181 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
4182 "stat_blocked and stat_runtime require the "
4183 "kernel parameter schedstats=enable or "
4184 "kernel.sched_schedstats=1\n");
4189 static inline bool cfs_bandwidth_used(void);
4196 * update_min_vruntime()
4197 * vruntime -= min_vruntime
4201 * update_min_vruntime()
4202 * vruntime += min_vruntime
4204 * this way the vruntime transition between RQs is done when both
4205 * min_vruntime are up-to-date.
4209 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
4210 * vruntime -= min_vruntime
4214 * update_min_vruntime()
4215 * vruntime += min_vruntime
4217 * this way we don't have the most up-to-date min_vruntime on the originating
4218 * CPU and an up-to-date min_vruntime on the destination CPU.
4222 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
4224 bool renorm
= !(flags
& ENQUEUE_WAKEUP
) || (flags
& ENQUEUE_MIGRATED
);
4225 bool curr
= cfs_rq
->curr
== se
;
4228 * If we're the current task, we must renormalise before calling
4232 se
->vruntime
+= cfs_rq
->min_vruntime
;
4234 update_curr(cfs_rq
);
4237 * Otherwise, renormalise after, such that we're placed at the current
4238 * moment in time, instead of some random moment in the past. Being
4239 * placed in the past could significantly boost this task to the
4240 * fairness detriment of existing tasks.
4242 if (renorm
&& !curr
)
4243 se
->vruntime
+= cfs_rq
->min_vruntime
;
4246 * When enqueuing a sched_entity, we must:
4247 * - Update loads to have both entity and cfs_rq synced with now.
4248 * - Add its load to cfs_rq->runnable_avg
4249 * - For group_entity, update its weight to reflect the new share of
4251 * - Add its new weight to cfs_rq->load.weight
4253 update_load_avg(cfs_rq
, se
, UPDATE_TG
| DO_ATTACH
);
4254 se_update_runnable(se
);
4255 update_cfs_group(se
);
4256 account_entity_enqueue(cfs_rq
, se
);
4258 if (flags
& ENQUEUE_WAKEUP
)
4259 place_entity(cfs_rq
, se
, 0);
4261 check_schedstat_required();
4262 update_stats_enqueue(cfs_rq
, se
, flags
);
4263 check_spread(cfs_rq
, se
);
4265 __enqueue_entity(cfs_rq
, se
);
4269 * When bandwidth control is enabled, cfs might have been removed
4270 * because of a parent been throttled but cfs->nr_running > 1. Try to
4271 * add it unconditionally.
4273 if (cfs_rq
->nr_running
== 1 || cfs_bandwidth_used())
4274 list_add_leaf_cfs_rq(cfs_rq
);
4276 if (cfs_rq
->nr_running
== 1)
4277 check_enqueue_throttle(cfs_rq
);
4280 static void __clear_buddies_last(struct sched_entity
*se
)
4282 for_each_sched_entity(se
) {
4283 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4284 if (cfs_rq
->last
!= se
)
4287 cfs_rq
->last
= NULL
;
4291 static void __clear_buddies_next(struct sched_entity
*se
)
4293 for_each_sched_entity(se
) {
4294 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4295 if (cfs_rq
->next
!= se
)
4298 cfs_rq
->next
= NULL
;
4302 static void __clear_buddies_skip(struct sched_entity
*se
)
4304 for_each_sched_entity(se
) {
4305 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4306 if (cfs_rq
->skip
!= se
)
4309 cfs_rq
->skip
= NULL
;
4313 static void clear_buddies(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
4315 if (cfs_rq
->last
== se
)
4316 __clear_buddies_last(se
);
4318 if (cfs_rq
->next
== se
)
4319 __clear_buddies_next(se
);
4321 if (cfs_rq
->skip
== se
)
4322 __clear_buddies_skip(se
);
4325 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
4328 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
4331 * Update run-time statistics of the 'current'.
4333 update_curr(cfs_rq
);
4336 * When dequeuing a sched_entity, we must:
4337 * - Update loads to have both entity and cfs_rq synced with now.
4338 * - Subtract its load from the cfs_rq->runnable_avg.
4339 * - Subtract its previous weight from cfs_rq->load.weight.
4340 * - For group entity, update its weight to reflect the new share
4341 * of its group cfs_rq.
4343 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
4344 se_update_runnable(se
);
4346 update_stats_dequeue(cfs_rq
, se
, flags
);
4348 clear_buddies(cfs_rq
, se
);
4350 if (se
!= cfs_rq
->curr
)
4351 __dequeue_entity(cfs_rq
, se
);
4353 account_entity_dequeue(cfs_rq
, se
);
4356 * Normalize after update_curr(); which will also have moved
4357 * min_vruntime if @se is the one holding it back. But before doing
4358 * update_min_vruntime() again, which will discount @se's position and
4359 * can move min_vruntime forward still more.
4361 if (!(flags
& DEQUEUE_SLEEP
))
4362 se
->vruntime
-= cfs_rq
->min_vruntime
;
4364 /* return excess runtime on last dequeue */
4365 return_cfs_rq_runtime(cfs_rq
);
4367 update_cfs_group(se
);
4370 * Now advance min_vruntime if @se was the entity holding it back,
4371 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
4372 * put back on, and if we advance min_vruntime, we'll be placed back
4373 * further than we started -- ie. we'll be penalized.
4375 if ((flags
& (DEQUEUE_SAVE
| DEQUEUE_MOVE
)) != DEQUEUE_SAVE
)
4376 update_min_vruntime(cfs_rq
);
4380 * Preempt the current task with a newly woken task if needed:
4383 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
4385 unsigned long ideal_runtime
, delta_exec
;
4386 struct sched_entity
*se
;
4389 ideal_runtime
= sched_slice(cfs_rq
, curr
);
4390 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
4391 if (delta_exec
> ideal_runtime
) {
4392 resched_curr(rq_of(cfs_rq
));
4394 * The current task ran long enough, ensure it doesn't get
4395 * re-elected due to buddy favours.
4397 clear_buddies(cfs_rq
, curr
);
4402 * Ensure that a task that missed wakeup preemption by a
4403 * narrow margin doesn't have to wait for a full slice.
4404 * This also mitigates buddy induced latencies under load.
4406 if (delta_exec
< sysctl_sched_min_granularity
)
4409 se
= __pick_first_entity(cfs_rq
);
4410 delta
= curr
->vruntime
- se
->vruntime
;
4415 if (delta
> ideal_runtime
)
4416 resched_curr(rq_of(cfs_rq
));
4420 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
4422 /* 'current' is not kept within the tree. */
4425 * Any task has to be enqueued before it get to execute on
4426 * a CPU. So account for the time it spent waiting on the
4429 update_stats_wait_end(cfs_rq
, se
);
4430 __dequeue_entity(cfs_rq
, se
);
4431 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
4434 update_stats_curr_start(cfs_rq
, se
);
4438 * Track our maximum slice length, if the CPU's load is at
4439 * least twice that of our own weight (i.e. dont track it
4440 * when there are only lesser-weight tasks around):
4442 if (schedstat_enabled() &&
4443 rq_of(cfs_rq
)->cfs
.load
.weight
>= 2*se
->load
.weight
) {
4444 schedstat_set(se
->statistics
.slice_max
,
4445 max((u64
)schedstat_val(se
->statistics
.slice_max
),
4446 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
));
4449 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
4453 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
);
4456 * Pick the next process, keeping these things in mind, in this order:
4457 * 1) keep things fair between processes/task groups
4458 * 2) pick the "next" process, since someone really wants that to run
4459 * 3) pick the "last" process, for cache locality
4460 * 4) do not run the "skip" process, if something else is available
4462 static struct sched_entity
*
4463 pick_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
4465 struct sched_entity
*left
= __pick_first_entity(cfs_rq
);
4466 struct sched_entity
*se
;
4469 * If curr is set we have to see if its left of the leftmost entity
4470 * still in the tree, provided there was anything in the tree at all.
4472 if (!left
|| (curr
&& entity_before(curr
, left
)))
4475 se
= left
; /* ideally we run the leftmost entity */
4478 * Avoid running the skip buddy, if running something else can
4479 * be done without getting too unfair.
4481 if (cfs_rq
->skip
== se
) {
4482 struct sched_entity
*second
;
4485 second
= __pick_first_entity(cfs_rq
);
4487 second
= __pick_next_entity(se
);
4488 if (!second
|| (curr
&& entity_before(curr
, second
)))
4492 if (second
&& wakeup_preempt_entity(second
, left
) < 1)
4496 if (cfs_rq
->next
&& wakeup_preempt_entity(cfs_rq
->next
, left
) < 1) {
4498 * Someone really wants this to run. If it's not unfair, run it.
4501 } else if (cfs_rq
->last
&& wakeup_preempt_entity(cfs_rq
->last
, left
) < 1) {
4503 * Prefer last buddy, try to return the CPU to a preempted task.
4508 clear_buddies(cfs_rq
, se
);
4513 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
4515 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
4518 * If still on the runqueue then deactivate_task()
4519 * was not called and update_curr() has to be done:
4522 update_curr(cfs_rq
);
4524 /* throttle cfs_rqs exceeding runtime */
4525 check_cfs_rq_runtime(cfs_rq
);
4527 check_spread(cfs_rq
, prev
);
4530 update_stats_wait_start(cfs_rq
, prev
);
4531 /* Put 'current' back into the tree. */
4532 __enqueue_entity(cfs_rq
, prev
);
4533 /* in !on_rq case, update occurred at dequeue */
4534 update_load_avg(cfs_rq
, prev
, 0);
4536 cfs_rq
->curr
= NULL
;
4540 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
4543 * Update run-time statistics of the 'current'.
4545 update_curr(cfs_rq
);
4548 * Ensure that runnable average is periodically updated.
4550 update_load_avg(cfs_rq
, curr
, UPDATE_TG
);
4551 update_cfs_group(curr
);
4553 #ifdef CONFIG_SCHED_HRTICK
4555 * queued ticks are scheduled to match the slice, so don't bother
4556 * validating it and just reschedule.
4559 resched_curr(rq_of(cfs_rq
));
4563 * don't let the period tick interfere with the hrtick preemption
4565 if (!sched_feat(DOUBLE_TICK
) &&
4566 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
4570 if (cfs_rq
->nr_running
> 1)
4571 check_preempt_tick(cfs_rq
, curr
);
4575 /**************************************************
4576 * CFS bandwidth control machinery
4579 #ifdef CONFIG_CFS_BANDWIDTH
4581 #ifdef CONFIG_JUMP_LABEL
4582 static struct static_key __cfs_bandwidth_used
;
4584 static inline bool cfs_bandwidth_used(void)
4586 return static_key_false(&__cfs_bandwidth_used
);
4589 void cfs_bandwidth_usage_inc(void)
4591 static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used
);
4594 void cfs_bandwidth_usage_dec(void)
4596 static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used
);
4598 #else /* CONFIG_JUMP_LABEL */
4599 static bool cfs_bandwidth_used(void)
4604 void cfs_bandwidth_usage_inc(void) {}
4605 void cfs_bandwidth_usage_dec(void) {}
4606 #endif /* CONFIG_JUMP_LABEL */
4609 * default period for cfs group bandwidth.
4610 * default: 0.1s, units: nanoseconds
4612 static inline u64
default_cfs_period(void)
4614 return 100000000ULL;
4617 static inline u64
sched_cfs_bandwidth_slice(void)
4619 return (u64
)sysctl_sched_cfs_bandwidth_slice
* NSEC_PER_USEC
;
4623 * Replenish runtime according to assigned quota. We use sched_clock_cpu
4624 * directly instead of rq->clock to avoid adding additional synchronization
4627 * requires cfs_b->lock
4629 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth
*cfs_b
)
4631 if (cfs_b
->quota
!= RUNTIME_INF
)
4632 cfs_b
->runtime
= cfs_b
->quota
;
4635 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
4637 return &tg
->cfs_bandwidth
;
4640 /* returns 0 on failure to allocate runtime */
4641 static int __assign_cfs_rq_runtime(struct cfs_bandwidth
*cfs_b
,
4642 struct cfs_rq
*cfs_rq
, u64 target_runtime
)
4644 u64 min_amount
, amount
= 0;
4646 lockdep_assert_held(&cfs_b
->lock
);
4648 /* note: this is a positive sum as runtime_remaining <= 0 */
4649 min_amount
= target_runtime
- cfs_rq
->runtime_remaining
;
4651 if (cfs_b
->quota
== RUNTIME_INF
)
4652 amount
= min_amount
;
4654 start_cfs_bandwidth(cfs_b
);
4656 if (cfs_b
->runtime
> 0) {
4657 amount
= min(cfs_b
->runtime
, min_amount
);
4658 cfs_b
->runtime
-= amount
;
4663 cfs_rq
->runtime_remaining
+= amount
;
4665 return cfs_rq
->runtime_remaining
> 0;
4668 /* returns 0 on failure to allocate runtime */
4669 static int assign_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4671 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4674 raw_spin_lock(&cfs_b
->lock
);
4675 ret
= __assign_cfs_rq_runtime(cfs_b
, cfs_rq
, sched_cfs_bandwidth_slice());
4676 raw_spin_unlock(&cfs_b
->lock
);
4681 static void __account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
4683 /* dock delta_exec before expiring quota (as it could span periods) */
4684 cfs_rq
->runtime_remaining
-= delta_exec
;
4686 if (likely(cfs_rq
->runtime_remaining
> 0))
4689 if (cfs_rq
->throttled
)
4692 * if we're unable to extend our runtime we resched so that the active
4693 * hierarchy can be throttled
4695 if (!assign_cfs_rq_runtime(cfs_rq
) && likely(cfs_rq
->curr
))
4696 resched_curr(rq_of(cfs_rq
));
4699 static __always_inline
4700 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
4702 if (!cfs_bandwidth_used() || !cfs_rq
->runtime_enabled
)
4705 __account_cfs_rq_runtime(cfs_rq
, delta_exec
);
4708 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
4710 return cfs_bandwidth_used() && cfs_rq
->throttled
;
4713 /* check whether cfs_rq, or any parent, is throttled */
4714 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
4716 return cfs_bandwidth_used() && cfs_rq
->throttle_count
;
4720 * Ensure that neither of the group entities corresponding to src_cpu or
4721 * dest_cpu are members of a throttled hierarchy when performing group
4722 * load-balance operations.
4724 static inline int throttled_lb_pair(struct task_group
*tg
,
4725 int src_cpu
, int dest_cpu
)
4727 struct cfs_rq
*src_cfs_rq
, *dest_cfs_rq
;
4729 src_cfs_rq
= tg
->cfs_rq
[src_cpu
];
4730 dest_cfs_rq
= tg
->cfs_rq
[dest_cpu
];
4732 return throttled_hierarchy(src_cfs_rq
) ||
4733 throttled_hierarchy(dest_cfs_rq
);
4736 static int tg_unthrottle_up(struct task_group
*tg
, void *data
)
4738 struct rq
*rq
= data
;
4739 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
4741 cfs_rq
->throttle_count
--;
4742 if (!cfs_rq
->throttle_count
) {
4743 cfs_rq
->throttled_clock_task_time
+= rq_clock_task(rq
) -
4744 cfs_rq
->throttled_clock_task
;
4746 /* Add cfs_rq with already running entity in the list */
4747 if (cfs_rq
->nr_running
>= 1)
4748 list_add_leaf_cfs_rq(cfs_rq
);
4754 static int tg_throttle_down(struct task_group
*tg
, void *data
)
4756 struct rq
*rq
= data
;
4757 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
4759 /* group is entering throttled state, stop time */
4760 if (!cfs_rq
->throttle_count
) {
4761 cfs_rq
->throttled_clock_task
= rq_clock_task(rq
);
4762 list_del_leaf_cfs_rq(cfs_rq
);
4764 cfs_rq
->throttle_count
++;
4769 static bool throttle_cfs_rq(struct cfs_rq
*cfs_rq
)
4771 struct rq
*rq
= rq_of(cfs_rq
);
4772 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4773 struct sched_entity
*se
;
4774 long task_delta
, idle_task_delta
, dequeue
= 1;
4776 raw_spin_lock(&cfs_b
->lock
);
4777 /* This will start the period timer if necessary */
4778 if (__assign_cfs_rq_runtime(cfs_b
, cfs_rq
, 1)) {
4780 * We have raced with bandwidth becoming available, and if we
4781 * actually throttled the timer might not unthrottle us for an
4782 * entire period. We additionally needed to make sure that any
4783 * subsequent check_cfs_rq_runtime calls agree not to throttle
4784 * us, as we may commit to do cfs put_prev+pick_next, so we ask
4785 * for 1ns of runtime rather than just check cfs_b.
4789 list_add_tail_rcu(&cfs_rq
->throttled_list
,
4790 &cfs_b
->throttled_cfs_rq
);
4792 raw_spin_unlock(&cfs_b
->lock
);
4795 return false; /* Throttle no longer required. */
4797 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
4799 /* freeze hierarchy runnable averages while throttled */
4801 walk_tg_tree_from(cfs_rq
->tg
, tg_throttle_down
, tg_nop
, (void *)rq
);
4804 task_delta
= cfs_rq
->h_nr_running
;
4805 idle_task_delta
= cfs_rq
->idle_h_nr_running
;
4806 for_each_sched_entity(se
) {
4807 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
4808 /* throttled entity or throttle-on-deactivate */
4812 dequeue_entity(qcfs_rq
, se
, DEQUEUE_SLEEP
);
4814 qcfs_rq
->h_nr_running
-= task_delta
;
4815 qcfs_rq
->idle_h_nr_running
-= idle_task_delta
;
4817 if (qcfs_rq
->load
.weight
) {
4818 /* Avoid re-evaluating load for this entity: */
4819 se
= parent_entity(se
);
4824 for_each_sched_entity(se
) {
4825 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
4826 /* throttled entity or throttle-on-deactivate */
4830 update_load_avg(qcfs_rq
, se
, 0);
4831 se_update_runnable(se
);
4833 qcfs_rq
->h_nr_running
-= task_delta
;
4834 qcfs_rq
->idle_h_nr_running
-= idle_task_delta
;
4837 /* At this point se is NULL and we are at root level*/
4838 sub_nr_running(rq
, task_delta
);
4842 * Note: distribution will already see us throttled via the
4843 * throttled-list. rq->lock protects completion.
4845 cfs_rq
->throttled
= 1;
4846 cfs_rq
->throttled_clock
= rq_clock(rq
);
4850 void unthrottle_cfs_rq(struct cfs_rq
*cfs_rq
)
4852 struct rq
*rq
= rq_of(cfs_rq
);
4853 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4854 struct sched_entity
*se
;
4855 long task_delta
, idle_task_delta
;
4857 se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
4859 cfs_rq
->throttled
= 0;
4861 update_rq_clock(rq
);
4863 raw_spin_lock(&cfs_b
->lock
);
4864 cfs_b
->throttled_time
+= rq_clock(rq
) - cfs_rq
->throttled_clock
;
4865 list_del_rcu(&cfs_rq
->throttled_list
);
4866 raw_spin_unlock(&cfs_b
->lock
);
4868 /* update hierarchical throttle state */
4869 walk_tg_tree_from(cfs_rq
->tg
, tg_nop
, tg_unthrottle_up
, (void *)rq
);
4871 if (!cfs_rq
->load
.weight
)
4874 task_delta
= cfs_rq
->h_nr_running
;
4875 idle_task_delta
= cfs_rq
->idle_h_nr_running
;
4876 for_each_sched_entity(se
) {
4879 cfs_rq
= cfs_rq_of(se
);
4880 enqueue_entity(cfs_rq
, se
, ENQUEUE_WAKEUP
);
4882 cfs_rq
->h_nr_running
+= task_delta
;
4883 cfs_rq
->idle_h_nr_running
+= idle_task_delta
;
4885 /* end evaluation on encountering a throttled cfs_rq */
4886 if (cfs_rq_throttled(cfs_rq
))
4887 goto unthrottle_throttle
;
4890 for_each_sched_entity(se
) {
4891 cfs_rq
= cfs_rq_of(se
);
4893 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
4894 se_update_runnable(se
);
4896 cfs_rq
->h_nr_running
+= task_delta
;
4897 cfs_rq
->idle_h_nr_running
+= idle_task_delta
;
4900 /* end evaluation on encountering a throttled cfs_rq */
4901 if (cfs_rq_throttled(cfs_rq
))
4902 goto unthrottle_throttle
;
4905 * One parent has been throttled and cfs_rq removed from the
4906 * list. Add it back to not break the leaf list.
4908 if (throttled_hierarchy(cfs_rq
))
4909 list_add_leaf_cfs_rq(cfs_rq
);
4912 /* At this point se is NULL and we are at root level*/
4913 add_nr_running(rq
, task_delta
);
4915 unthrottle_throttle
:
4917 * The cfs_rq_throttled() breaks in the above iteration can result in
4918 * incomplete leaf list maintenance, resulting in triggering the
4921 for_each_sched_entity(se
) {
4922 cfs_rq
= cfs_rq_of(se
);
4924 if (list_add_leaf_cfs_rq(cfs_rq
))
4928 assert_list_leaf_cfs_rq(rq
);
4930 /* Determine whether we need to wake up potentially idle CPU: */
4931 if (rq
->curr
== rq
->idle
&& rq
->cfs
.nr_running
)
4935 static void distribute_cfs_runtime(struct cfs_bandwidth
*cfs_b
)
4937 struct cfs_rq
*cfs_rq
;
4938 u64 runtime
, remaining
= 1;
4941 list_for_each_entry_rcu(cfs_rq
, &cfs_b
->throttled_cfs_rq
,
4943 struct rq
*rq
= rq_of(cfs_rq
);
4946 rq_lock_irqsave(rq
, &rf
);
4947 if (!cfs_rq_throttled(cfs_rq
))
4950 /* By the above check, this should never be true */
4951 SCHED_WARN_ON(cfs_rq
->runtime_remaining
> 0);
4953 raw_spin_lock(&cfs_b
->lock
);
4954 runtime
= -cfs_rq
->runtime_remaining
+ 1;
4955 if (runtime
> cfs_b
->runtime
)
4956 runtime
= cfs_b
->runtime
;
4957 cfs_b
->runtime
-= runtime
;
4958 remaining
= cfs_b
->runtime
;
4959 raw_spin_unlock(&cfs_b
->lock
);
4961 cfs_rq
->runtime_remaining
+= runtime
;
4963 /* we check whether we're throttled above */
4964 if (cfs_rq
->runtime_remaining
> 0)
4965 unthrottle_cfs_rq(cfs_rq
);
4968 rq_unlock_irqrestore(rq
, &rf
);
4977 * Responsible for refilling a task_group's bandwidth and unthrottling its
4978 * cfs_rqs as appropriate. If there has been no activity within the last
4979 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
4980 * used to track this state.
4982 static int do_sched_cfs_period_timer(struct cfs_bandwidth
*cfs_b
, int overrun
, unsigned long flags
)
4986 /* no need to continue the timer with no bandwidth constraint */
4987 if (cfs_b
->quota
== RUNTIME_INF
)
4988 goto out_deactivate
;
4990 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
4991 cfs_b
->nr_periods
+= overrun
;
4994 * idle depends on !throttled (for the case of a large deficit), and if
4995 * we're going inactive then everything else can be deferred
4997 if (cfs_b
->idle
&& !throttled
)
4998 goto out_deactivate
;
5000 __refill_cfs_bandwidth_runtime(cfs_b
);
5003 /* mark as potentially idle for the upcoming period */
5008 /* account preceding periods in which throttling occurred */
5009 cfs_b
->nr_throttled
+= overrun
;
5012 * This check is repeated as we release cfs_b->lock while we unthrottle.
5014 while (throttled
&& cfs_b
->runtime
> 0) {
5015 raw_spin_unlock_irqrestore(&cfs_b
->lock
, flags
);
5016 /* we can't nest cfs_b->lock while distributing bandwidth */
5017 distribute_cfs_runtime(cfs_b
);
5018 raw_spin_lock_irqsave(&cfs_b
->lock
, flags
);
5020 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
5024 * While we are ensured activity in the period following an
5025 * unthrottle, this also covers the case in which the new bandwidth is
5026 * insufficient to cover the existing bandwidth deficit. (Forcing the
5027 * timer to remain active while there are any throttled entities.)
5037 /* a cfs_rq won't donate quota below this amount */
5038 static const u64 min_cfs_rq_runtime
= 1 * NSEC_PER_MSEC
;
5039 /* minimum remaining period time to redistribute slack quota */
5040 static const u64 min_bandwidth_expiration
= 2 * NSEC_PER_MSEC
;
5041 /* how long we wait to gather additional slack before distributing */
5042 static const u64 cfs_bandwidth_slack_period
= 5 * NSEC_PER_MSEC
;
5045 * Are we near the end of the current quota period?
5047 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
5048 * hrtimer base being cleared by hrtimer_start. In the case of
5049 * migrate_hrtimers, base is never cleared, so we are fine.
5051 static int runtime_refresh_within(struct cfs_bandwidth
*cfs_b
, u64 min_expire
)
5053 struct hrtimer
*refresh_timer
= &cfs_b
->period_timer
;
5056 /* if the call-back is running a quota refresh is already occurring */
5057 if (hrtimer_callback_running(refresh_timer
))
5060 /* is a quota refresh about to occur? */
5061 remaining
= ktime_to_ns(hrtimer_expires_remaining(refresh_timer
));
5062 if (remaining
< min_expire
)
5068 static void start_cfs_slack_bandwidth(struct cfs_bandwidth
*cfs_b
)
5070 u64 min_left
= cfs_bandwidth_slack_period
+ min_bandwidth_expiration
;
5072 /* if there's a quota refresh soon don't bother with slack */
5073 if (runtime_refresh_within(cfs_b
, min_left
))
5076 /* don't push forwards an existing deferred unthrottle */
5077 if (cfs_b
->slack_started
)
5079 cfs_b
->slack_started
= true;
5081 hrtimer_start(&cfs_b
->slack_timer
,
5082 ns_to_ktime(cfs_bandwidth_slack_period
),
5086 /* we know any runtime found here is valid as update_curr() precedes return */
5087 static void __return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
5089 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
5090 s64 slack_runtime
= cfs_rq
->runtime_remaining
- min_cfs_rq_runtime
;
5092 if (slack_runtime
<= 0)
5095 raw_spin_lock(&cfs_b
->lock
);
5096 if (cfs_b
->quota
!= RUNTIME_INF
) {
5097 cfs_b
->runtime
+= slack_runtime
;
5099 /* we are under rq->lock, defer unthrottling using a timer */
5100 if (cfs_b
->runtime
> sched_cfs_bandwidth_slice() &&
5101 !list_empty(&cfs_b
->throttled_cfs_rq
))
5102 start_cfs_slack_bandwidth(cfs_b
);
5104 raw_spin_unlock(&cfs_b
->lock
);
5106 /* even if it's not valid for return we don't want to try again */
5107 cfs_rq
->runtime_remaining
-= slack_runtime
;
5110 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
5112 if (!cfs_bandwidth_used())
5115 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->nr_running
)
5118 __return_cfs_rq_runtime(cfs_rq
);
5122 * This is done with a timer (instead of inline with bandwidth return) since
5123 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
5125 static void do_sched_cfs_slack_timer(struct cfs_bandwidth
*cfs_b
)
5127 u64 runtime
= 0, slice
= sched_cfs_bandwidth_slice();
5128 unsigned long flags
;
5130 /* confirm we're still not at a refresh boundary */
5131 raw_spin_lock_irqsave(&cfs_b
->lock
, flags
);
5132 cfs_b
->slack_started
= false;
5134 if (runtime_refresh_within(cfs_b
, min_bandwidth_expiration
)) {
5135 raw_spin_unlock_irqrestore(&cfs_b
->lock
, flags
);
5139 if (cfs_b
->quota
!= RUNTIME_INF
&& cfs_b
->runtime
> slice
)
5140 runtime
= cfs_b
->runtime
;
5142 raw_spin_unlock_irqrestore(&cfs_b
->lock
, flags
);
5147 distribute_cfs_runtime(cfs_b
);
5151 * When a group wakes up we want to make sure that its quota is not already
5152 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
5153 * runtime as update_curr() throttling can not trigger until it's on-rq.
5155 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
)
5157 if (!cfs_bandwidth_used())
5160 /* an active group must be handled by the update_curr()->put() path */
5161 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->curr
)
5164 /* ensure the group is not already throttled */
5165 if (cfs_rq_throttled(cfs_rq
))
5168 /* update runtime allocation */
5169 account_cfs_rq_runtime(cfs_rq
, 0);
5170 if (cfs_rq
->runtime_remaining
<= 0)
5171 throttle_cfs_rq(cfs_rq
);
5174 static void sync_throttle(struct task_group
*tg
, int cpu
)
5176 struct cfs_rq
*pcfs_rq
, *cfs_rq
;
5178 if (!cfs_bandwidth_used())
5184 cfs_rq
= tg
->cfs_rq
[cpu
];
5185 pcfs_rq
= tg
->parent
->cfs_rq
[cpu
];
5187 cfs_rq
->throttle_count
= pcfs_rq
->throttle_count
;
5188 cfs_rq
->throttled_clock_task
= rq_clock_task(cpu_rq(cpu
));
5191 /* conditionally throttle active cfs_rq's from put_prev_entity() */
5192 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
5194 if (!cfs_bandwidth_used())
5197 if (likely(!cfs_rq
->runtime_enabled
|| cfs_rq
->runtime_remaining
> 0))
5201 * it's possible for a throttled entity to be forced into a running
5202 * state (e.g. set_curr_task), in this case we're finished.
5204 if (cfs_rq_throttled(cfs_rq
))
5207 return throttle_cfs_rq(cfs_rq
);
5210 static enum hrtimer_restart
sched_cfs_slack_timer(struct hrtimer
*timer
)
5212 struct cfs_bandwidth
*cfs_b
=
5213 container_of(timer
, struct cfs_bandwidth
, slack_timer
);
5215 do_sched_cfs_slack_timer(cfs_b
);
5217 return HRTIMER_NORESTART
;
5220 extern const u64 max_cfs_quota_period
;
5222 static enum hrtimer_restart
sched_cfs_period_timer(struct hrtimer
*timer
)
5224 struct cfs_bandwidth
*cfs_b
=
5225 container_of(timer
, struct cfs_bandwidth
, period_timer
);
5226 unsigned long flags
;
5231 raw_spin_lock_irqsave(&cfs_b
->lock
, flags
);
5233 overrun
= hrtimer_forward_now(timer
, cfs_b
->period
);
5237 idle
= do_sched_cfs_period_timer(cfs_b
, overrun
, flags
);
5240 u64
new, old
= ktime_to_ns(cfs_b
->period
);
5243 * Grow period by a factor of 2 to avoid losing precision.
5244 * Precision loss in the quota/period ratio can cause __cfs_schedulable
5248 if (new < max_cfs_quota_period
) {
5249 cfs_b
->period
= ns_to_ktime(new);
5252 pr_warn_ratelimited(
5253 "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
5255 div_u64(new, NSEC_PER_USEC
),
5256 div_u64(cfs_b
->quota
, NSEC_PER_USEC
));
5258 pr_warn_ratelimited(
5259 "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
5261 div_u64(old
, NSEC_PER_USEC
),
5262 div_u64(cfs_b
->quota
, NSEC_PER_USEC
));
5265 /* reset count so we don't come right back in here */
5270 cfs_b
->period_active
= 0;
5271 raw_spin_unlock_irqrestore(&cfs_b
->lock
, flags
);
5273 return idle
? HRTIMER_NORESTART
: HRTIMER_RESTART
;
5276 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
5278 raw_spin_lock_init(&cfs_b
->lock
);
5280 cfs_b
->quota
= RUNTIME_INF
;
5281 cfs_b
->period
= ns_to_ktime(default_cfs_period());
5283 INIT_LIST_HEAD(&cfs_b
->throttled_cfs_rq
);
5284 hrtimer_init(&cfs_b
->period_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS_PINNED
);
5285 cfs_b
->period_timer
.function
= sched_cfs_period_timer
;
5286 hrtimer_init(&cfs_b
->slack_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
5287 cfs_b
->slack_timer
.function
= sched_cfs_slack_timer
;
5288 cfs_b
->slack_started
= false;
5291 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
5293 cfs_rq
->runtime_enabled
= 0;
5294 INIT_LIST_HEAD(&cfs_rq
->throttled_list
);
5297 void start_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
5299 lockdep_assert_held(&cfs_b
->lock
);
5301 if (cfs_b
->period_active
)
5304 cfs_b
->period_active
= 1;
5305 hrtimer_forward_now(&cfs_b
->period_timer
, cfs_b
->period
);
5306 hrtimer_start_expires(&cfs_b
->period_timer
, HRTIMER_MODE_ABS_PINNED
);
5309 static void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
5311 /* init_cfs_bandwidth() was not called */
5312 if (!cfs_b
->throttled_cfs_rq
.next
)
5315 hrtimer_cancel(&cfs_b
->period_timer
);
5316 hrtimer_cancel(&cfs_b
->slack_timer
);
5320 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
5322 * The race is harmless, since modifying bandwidth settings of unhooked group
5323 * bits doesn't do much.
5326 /* cpu online callback */
5327 static void __maybe_unused
update_runtime_enabled(struct rq
*rq
)
5329 struct task_group
*tg
;
5331 lockdep_assert_held(&rq
->lock
);
5334 list_for_each_entry_rcu(tg
, &task_groups
, list
) {
5335 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
5336 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
5338 raw_spin_lock(&cfs_b
->lock
);
5339 cfs_rq
->runtime_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
5340 raw_spin_unlock(&cfs_b
->lock
);
5345 /* cpu offline callback */
5346 static void __maybe_unused
unthrottle_offline_cfs_rqs(struct rq
*rq
)
5348 struct task_group
*tg
;
5350 lockdep_assert_held(&rq
->lock
);
5353 list_for_each_entry_rcu(tg
, &task_groups
, list
) {
5354 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
5356 if (!cfs_rq
->runtime_enabled
)
5360 * clock_task is not advancing so we just need to make sure
5361 * there's some valid quota amount
5363 cfs_rq
->runtime_remaining
= 1;
5365 * Offline rq is schedulable till CPU is completely disabled
5366 * in take_cpu_down(), so we prevent new cfs throttling here.
5368 cfs_rq
->runtime_enabled
= 0;
5370 if (cfs_rq_throttled(cfs_rq
))
5371 unthrottle_cfs_rq(cfs_rq
);
5376 #else /* CONFIG_CFS_BANDWIDTH */
5378 static inline bool cfs_bandwidth_used(void)
5383 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
) {}
5384 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) { return false; }
5385 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
) {}
5386 static inline void sync_throttle(struct task_group
*tg
, int cpu
) {}
5387 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
5389 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
5394 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
5399 static inline int throttled_lb_pair(struct task_group
*tg
,
5400 int src_cpu
, int dest_cpu
)
5405 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
5407 #ifdef CONFIG_FAIR_GROUP_SCHED
5408 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
5411 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
5415 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
5416 static inline void update_runtime_enabled(struct rq
*rq
) {}
5417 static inline void unthrottle_offline_cfs_rqs(struct rq
*rq
) {}
5419 #endif /* CONFIG_CFS_BANDWIDTH */
5421 /**************************************************
5422 * CFS operations on tasks:
5425 #ifdef CONFIG_SCHED_HRTICK
5426 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
5428 struct sched_entity
*se
= &p
->se
;
5429 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
5431 SCHED_WARN_ON(task_rq(p
) != rq
);
5433 if (rq
->cfs
.h_nr_running
> 1) {
5434 u64 slice
= sched_slice(cfs_rq
, se
);
5435 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
5436 s64 delta
= slice
- ran
;
5439 if (task_current(rq
, p
))
5443 hrtick_start(rq
, delta
);
5448 * called from enqueue/dequeue and updates the hrtick when the
5449 * current task is from our class and nr_running is low enough
5452 static void hrtick_update(struct rq
*rq
)
5454 struct task_struct
*curr
= rq
->curr
;
5456 if (!hrtick_enabled_fair(rq
) || curr
->sched_class
!= &fair_sched_class
)
5459 if (cfs_rq_of(&curr
->se
)->nr_running
< sched_nr_latency
)
5460 hrtick_start_fair(rq
, curr
);
5462 #else /* !CONFIG_SCHED_HRTICK */
5464 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
5468 static inline void hrtick_update(struct rq
*rq
)
5474 static inline unsigned long cpu_util(int cpu
);
5476 static inline bool cpu_overutilized(int cpu
)
5478 return !fits_capacity(cpu_util(cpu
), capacity_of(cpu
));
5481 static inline void update_overutilized_status(struct rq
*rq
)
5483 if (!READ_ONCE(rq
->rd
->overutilized
) && cpu_overutilized(rq
->cpu
)) {
5484 WRITE_ONCE(rq
->rd
->overutilized
, SG_OVERUTILIZED
);
5485 trace_sched_overutilized_tp(rq
->rd
, SG_OVERUTILIZED
);
5489 static inline void update_overutilized_status(struct rq
*rq
) { }
5492 /* Runqueue only has SCHED_IDLE tasks enqueued */
5493 static int sched_idle_rq(struct rq
*rq
)
5495 return unlikely(rq
->nr_running
== rq
->cfs
.idle_h_nr_running
&&
5500 static int sched_idle_cpu(int cpu
)
5502 return sched_idle_rq(cpu_rq(cpu
));
5507 * The enqueue_task method is called before nr_running is
5508 * increased. Here we update the fair scheduling stats and
5509 * then put the task into the rbtree:
5512 enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
5514 struct cfs_rq
*cfs_rq
;
5515 struct sched_entity
*se
= &p
->se
;
5516 int idle_h_nr_running
= task_has_idle_policy(p
);
5517 int task_new
= !(flags
& ENQUEUE_WAKEUP
);
5520 * The code below (indirectly) updates schedutil which looks at
5521 * the cfs_rq utilization to select a frequency.
5522 * Let's add the task's estimated utilization to the cfs_rq's
5523 * estimated utilization, before we update schedutil.
5525 util_est_enqueue(&rq
->cfs
, p
);
5528 * If in_iowait is set, the code below may not trigger any cpufreq
5529 * utilization updates, so do it here explicitly with the IOWAIT flag
5533 cpufreq_update_util(rq
, SCHED_CPUFREQ_IOWAIT
);
5535 for_each_sched_entity(se
) {
5538 cfs_rq
= cfs_rq_of(se
);
5539 enqueue_entity(cfs_rq
, se
, flags
);
5541 cfs_rq
->h_nr_running
++;
5542 cfs_rq
->idle_h_nr_running
+= idle_h_nr_running
;
5544 /* end evaluation on encountering a throttled cfs_rq */
5545 if (cfs_rq_throttled(cfs_rq
))
5546 goto enqueue_throttle
;
5548 flags
= ENQUEUE_WAKEUP
;
5551 for_each_sched_entity(se
) {
5552 cfs_rq
= cfs_rq_of(se
);
5554 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
5555 se_update_runnable(se
);
5556 update_cfs_group(se
);
5558 cfs_rq
->h_nr_running
++;
5559 cfs_rq
->idle_h_nr_running
+= idle_h_nr_running
;
5561 /* end evaluation on encountering a throttled cfs_rq */
5562 if (cfs_rq_throttled(cfs_rq
))
5563 goto enqueue_throttle
;
5566 * One parent has been throttled and cfs_rq removed from the
5567 * list. Add it back to not break the leaf list.
5569 if (throttled_hierarchy(cfs_rq
))
5570 list_add_leaf_cfs_rq(cfs_rq
);
5573 /* At this point se is NULL and we are at root level*/
5574 add_nr_running(rq
, 1);
5577 * Since new tasks are assigned an initial util_avg equal to
5578 * half of the spare capacity of their CPU, tiny tasks have the
5579 * ability to cross the overutilized threshold, which will
5580 * result in the load balancer ruining all the task placement
5581 * done by EAS. As a way to mitigate that effect, do not account
5582 * for the first enqueue operation of new tasks during the
5583 * overutilized flag detection.
5585 * A better way of solving this problem would be to wait for
5586 * the PELT signals of tasks to converge before taking them
5587 * into account, but that is not straightforward to implement,
5588 * and the following generally works well enough in practice.
5591 update_overutilized_status(rq
);
5594 if (cfs_bandwidth_used()) {
5596 * When bandwidth control is enabled; the cfs_rq_throttled()
5597 * breaks in the above iteration can result in incomplete
5598 * leaf list maintenance, resulting in triggering the assertion
5601 for_each_sched_entity(se
) {
5602 cfs_rq
= cfs_rq_of(se
);
5604 if (list_add_leaf_cfs_rq(cfs_rq
))
5609 assert_list_leaf_cfs_rq(rq
);
5614 static void set_next_buddy(struct sched_entity
*se
);
5617 * The dequeue_task method is called before nr_running is
5618 * decreased. We remove the task from the rbtree and
5619 * update the fair scheduling stats:
5621 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
5623 struct cfs_rq
*cfs_rq
;
5624 struct sched_entity
*se
= &p
->se
;
5625 int task_sleep
= flags
& DEQUEUE_SLEEP
;
5626 int idle_h_nr_running
= task_has_idle_policy(p
);
5627 bool was_sched_idle
= sched_idle_rq(rq
);
5629 util_est_dequeue(&rq
->cfs
, p
);
5631 for_each_sched_entity(se
) {
5632 cfs_rq
= cfs_rq_of(se
);
5633 dequeue_entity(cfs_rq
, se
, flags
);
5635 cfs_rq
->h_nr_running
--;
5636 cfs_rq
->idle_h_nr_running
-= idle_h_nr_running
;
5638 /* end evaluation on encountering a throttled cfs_rq */
5639 if (cfs_rq_throttled(cfs_rq
))
5640 goto dequeue_throttle
;
5642 /* Don't dequeue parent if it has other entities besides us */
5643 if (cfs_rq
->load
.weight
) {
5644 /* Avoid re-evaluating load for this entity: */
5645 se
= parent_entity(se
);
5647 * Bias pick_next to pick a task from this cfs_rq, as
5648 * p is sleeping when it is within its sched_slice.
5650 if (task_sleep
&& se
&& !throttled_hierarchy(cfs_rq
))
5654 flags
|= DEQUEUE_SLEEP
;
5657 for_each_sched_entity(se
) {
5658 cfs_rq
= cfs_rq_of(se
);
5660 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
5661 se_update_runnable(se
);
5662 update_cfs_group(se
);
5664 cfs_rq
->h_nr_running
--;
5665 cfs_rq
->idle_h_nr_running
-= idle_h_nr_running
;
5667 /* end evaluation on encountering a throttled cfs_rq */
5668 if (cfs_rq_throttled(cfs_rq
))
5669 goto dequeue_throttle
;
5673 /* At this point se is NULL and we are at root level*/
5674 sub_nr_running(rq
, 1);
5676 /* balance early to pull high priority tasks */
5677 if (unlikely(!was_sched_idle
&& sched_idle_rq(rq
)))
5678 rq
->next_balance
= jiffies
;
5681 util_est_update(&rq
->cfs
, p
, task_sleep
);
5687 /* Working cpumask for: load_balance, load_balance_newidle. */
5688 DEFINE_PER_CPU(cpumask_var_t
, load_balance_mask
);
5689 DEFINE_PER_CPU(cpumask_var_t
, select_idle_mask
);
5691 #ifdef CONFIG_NO_HZ_COMMON
5694 cpumask_var_t idle_cpus_mask
;
5696 int has_blocked
; /* Idle CPUS has blocked load */
5697 unsigned long next_balance
; /* in jiffy units */
5698 unsigned long next_blocked
; /* Next update of blocked load in jiffies */
5699 } nohz ____cacheline_aligned
;
5701 #endif /* CONFIG_NO_HZ_COMMON */
5703 static unsigned long cpu_load(struct rq
*rq
)
5705 return cfs_rq_load_avg(&rq
->cfs
);
5709 * cpu_load_without - compute CPU load without any contributions from *p
5710 * @cpu: the CPU which load is requested
5711 * @p: the task which load should be discounted
5713 * The load of a CPU is defined by the load of tasks currently enqueued on that
5714 * CPU as well as tasks which are currently sleeping after an execution on that
5717 * This method returns the load of the specified CPU by discounting the load of
5718 * the specified task, whenever the task is currently contributing to the CPU
5721 static unsigned long cpu_load_without(struct rq
*rq
, struct task_struct
*p
)
5723 struct cfs_rq
*cfs_rq
;
5726 /* Task has no contribution or is new */
5727 if (cpu_of(rq
) != task_cpu(p
) || !READ_ONCE(p
->se
.avg
.last_update_time
))
5728 return cpu_load(rq
);
5731 load
= READ_ONCE(cfs_rq
->avg
.load_avg
);
5733 /* Discount task's util from CPU's util */
5734 lsub_positive(&load
, task_h_load(p
));
5739 static unsigned long cpu_runnable(struct rq
*rq
)
5741 return cfs_rq_runnable_avg(&rq
->cfs
);
5744 static unsigned long cpu_runnable_without(struct rq
*rq
, struct task_struct
*p
)
5746 struct cfs_rq
*cfs_rq
;
5747 unsigned int runnable
;
5749 /* Task has no contribution or is new */
5750 if (cpu_of(rq
) != task_cpu(p
) || !READ_ONCE(p
->se
.avg
.last_update_time
))
5751 return cpu_runnable(rq
);
5754 runnable
= READ_ONCE(cfs_rq
->avg
.runnable_avg
);
5756 /* Discount task's runnable from CPU's runnable */
5757 lsub_positive(&runnable
, p
->se
.avg
.runnable_avg
);
5762 static unsigned long capacity_of(int cpu
)
5764 return cpu_rq(cpu
)->cpu_capacity
;
5767 static void record_wakee(struct task_struct
*p
)
5770 * Only decay a single time; tasks that have less then 1 wakeup per
5771 * jiffy will not have built up many flips.
5773 if (time_after(jiffies
, current
->wakee_flip_decay_ts
+ HZ
)) {
5774 current
->wakee_flips
>>= 1;
5775 current
->wakee_flip_decay_ts
= jiffies
;
5778 if (current
->last_wakee
!= p
) {
5779 current
->last_wakee
= p
;
5780 current
->wakee_flips
++;
5785 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5787 * A waker of many should wake a different task than the one last awakened
5788 * at a frequency roughly N times higher than one of its wakees.
5790 * In order to determine whether we should let the load spread vs consolidating
5791 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5792 * partner, and a factor of lls_size higher frequency in the other.
5794 * With both conditions met, we can be relatively sure that the relationship is
5795 * non-monogamous, with partner count exceeding socket size.
5797 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5798 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5801 static int wake_wide(struct task_struct
*p
)
5803 unsigned int master
= current
->wakee_flips
;
5804 unsigned int slave
= p
->wakee_flips
;
5805 int factor
= __this_cpu_read(sd_llc_size
);
5808 swap(master
, slave
);
5809 if (slave
< factor
|| master
< slave
* factor
)
5815 * The purpose of wake_affine() is to quickly determine on which CPU we can run
5816 * soonest. For the purpose of speed we only consider the waking and previous
5819 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
5820 * cache-affine and is (or will be) idle.
5822 * wake_affine_weight() - considers the weight to reflect the average
5823 * scheduling latency of the CPUs. This seems to work
5824 * for the overloaded case.
5827 wake_affine_idle(int this_cpu
, int prev_cpu
, int sync
)
5830 * If this_cpu is idle, it implies the wakeup is from interrupt
5831 * context. Only allow the move if cache is shared. Otherwise an
5832 * interrupt intensive workload could force all tasks onto one
5833 * node depending on the IO topology or IRQ affinity settings.
5835 * If the prev_cpu is idle and cache affine then avoid a migration.
5836 * There is no guarantee that the cache hot data from an interrupt
5837 * is more important than cache hot data on the prev_cpu and from
5838 * a cpufreq perspective, it's better to have higher utilisation
5841 if (available_idle_cpu(this_cpu
) && cpus_share_cache(this_cpu
, prev_cpu
))
5842 return available_idle_cpu(prev_cpu
) ? prev_cpu
: this_cpu
;
5844 if (sync
&& cpu_rq(this_cpu
)->nr_running
== 1)
5847 if (available_idle_cpu(prev_cpu
))
5850 return nr_cpumask_bits
;
5854 wake_affine_weight(struct sched_domain
*sd
, struct task_struct
*p
,
5855 int this_cpu
, int prev_cpu
, int sync
)
5857 s64 this_eff_load
, prev_eff_load
;
5858 unsigned long task_load
;
5860 this_eff_load
= cpu_load(cpu_rq(this_cpu
));
5863 unsigned long current_load
= task_h_load(current
);
5865 if (current_load
> this_eff_load
)
5868 this_eff_load
-= current_load
;
5871 task_load
= task_h_load(p
);
5873 this_eff_load
+= task_load
;
5874 if (sched_feat(WA_BIAS
))
5875 this_eff_load
*= 100;
5876 this_eff_load
*= capacity_of(prev_cpu
);
5878 prev_eff_load
= cpu_load(cpu_rq(prev_cpu
));
5879 prev_eff_load
-= task_load
;
5880 if (sched_feat(WA_BIAS
))
5881 prev_eff_load
*= 100 + (sd
->imbalance_pct
- 100) / 2;
5882 prev_eff_load
*= capacity_of(this_cpu
);
5885 * If sync, adjust the weight of prev_eff_load such that if
5886 * prev_eff == this_eff that select_idle_sibling() will consider
5887 * stacking the wakee on top of the waker if no other CPU is
5893 return this_eff_load
< prev_eff_load
? this_cpu
: nr_cpumask_bits
;
5896 static int wake_affine(struct sched_domain
*sd
, struct task_struct
*p
,
5897 int this_cpu
, int prev_cpu
, int sync
)
5899 int target
= nr_cpumask_bits
;
5901 if (sched_feat(WA_IDLE
))
5902 target
= wake_affine_idle(this_cpu
, prev_cpu
, sync
);
5904 if (sched_feat(WA_WEIGHT
) && target
== nr_cpumask_bits
)
5905 target
= wake_affine_weight(sd
, p
, this_cpu
, prev_cpu
, sync
);
5907 schedstat_inc(p
->se
.statistics
.nr_wakeups_affine_attempts
);
5908 if (target
== nr_cpumask_bits
)
5911 schedstat_inc(sd
->ttwu_move_affine
);
5912 schedstat_inc(p
->se
.statistics
.nr_wakeups_affine
);
5916 static struct sched_group
*
5917 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
, int this_cpu
);
5920 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
5923 find_idlest_group_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
5925 unsigned long load
, min_load
= ULONG_MAX
;
5926 unsigned int min_exit_latency
= UINT_MAX
;
5927 u64 latest_idle_timestamp
= 0;
5928 int least_loaded_cpu
= this_cpu
;
5929 int shallowest_idle_cpu
= -1;
5932 /* Check if we have any choice: */
5933 if (group
->group_weight
== 1)
5934 return cpumask_first(sched_group_span(group
));
5936 /* Traverse only the allowed CPUs */
5937 for_each_cpu_and(i
, sched_group_span(group
), p
->cpus_ptr
) {
5938 if (sched_idle_cpu(i
))
5941 if (available_idle_cpu(i
)) {
5942 struct rq
*rq
= cpu_rq(i
);
5943 struct cpuidle_state
*idle
= idle_get_state(rq
);
5944 if (idle
&& idle
->exit_latency
< min_exit_latency
) {
5946 * We give priority to a CPU whose idle state
5947 * has the smallest exit latency irrespective
5948 * of any idle timestamp.
5950 min_exit_latency
= idle
->exit_latency
;
5951 latest_idle_timestamp
= rq
->idle_stamp
;
5952 shallowest_idle_cpu
= i
;
5953 } else if ((!idle
|| idle
->exit_latency
== min_exit_latency
) &&
5954 rq
->idle_stamp
> latest_idle_timestamp
) {
5956 * If equal or no active idle state, then
5957 * the most recently idled CPU might have
5960 latest_idle_timestamp
= rq
->idle_stamp
;
5961 shallowest_idle_cpu
= i
;
5963 } else if (shallowest_idle_cpu
== -1) {
5964 load
= cpu_load(cpu_rq(i
));
5965 if (load
< min_load
) {
5967 least_loaded_cpu
= i
;
5972 return shallowest_idle_cpu
!= -1 ? shallowest_idle_cpu
: least_loaded_cpu
;
5975 static inline int find_idlest_cpu(struct sched_domain
*sd
, struct task_struct
*p
,
5976 int cpu
, int prev_cpu
, int sd_flag
)
5980 if (!cpumask_intersects(sched_domain_span(sd
), p
->cpus_ptr
))
5984 * We need task's util for cpu_util_without, sync it up to
5985 * prev_cpu's last_update_time.
5987 if (!(sd_flag
& SD_BALANCE_FORK
))
5988 sync_entity_load_avg(&p
->se
);
5991 struct sched_group
*group
;
5992 struct sched_domain
*tmp
;
5995 if (!(sd
->flags
& sd_flag
)) {
6000 group
= find_idlest_group(sd
, p
, cpu
);
6006 new_cpu
= find_idlest_group_cpu(group
, p
, cpu
);
6007 if (new_cpu
== cpu
) {
6008 /* Now try balancing at a lower domain level of 'cpu': */
6013 /* Now try balancing at a lower domain level of 'new_cpu': */
6015 weight
= sd
->span_weight
;
6017 for_each_domain(cpu
, tmp
) {
6018 if (weight
<= tmp
->span_weight
)
6020 if (tmp
->flags
& sd_flag
)
6028 static inline int __select_idle_cpu(int cpu
)
6030 if (available_idle_cpu(cpu
) || sched_idle_cpu(cpu
))
6036 #ifdef CONFIG_SCHED_SMT
6037 DEFINE_STATIC_KEY_FALSE(sched_smt_present
);
6038 EXPORT_SYMBOL_GPL(sched_smt_present
);
6040 static inline void set_idle_cores(int cpu
, int val
)
6042 struct sched_domain_shared
*sds
;
6044 sds
= rcu_dereference(per_cpu(sd_llc_shared
, cpu
));
6046 WRITE_ONCE(sds
->has_idle_cores
, val
);
6049 static inline bool test_idle_cores(int cpu
, bool def
)
6051 struct sched_domain_shared
*sds
;
6053 sds
= rcu_dereference(per_cpu(sd_llc_shared
, cpu
));
6055 return READ_ONCE(sds
->has_idle_cores
);
6061 * Scans the local SMT mask to see if the entire core is idle, and records this
6062 * information in sd_llc_shared->has_idle_cores.
6064 * Since SMT siblings share all cache levels, inspecting this limited remote
6065 * state should be fairly cheap.
6067 void __update_idle_core(struct rq
*rq
)
6069 int core
= cpu_of(rq
);
6073 if (test_idle_cores(core
, true))
6076 for_each_cpu(cpu
, cpu_smt_mask(core
)) {
6080 if (!available_idle_cpu(cpu
))
6084 set_idle_cores(core
, 1);
6090 * Scan the entire LLC domain for idle cores; this dynamically switches off if
6091 * there are no idle cores left in the system; tracked through
6092 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
6094 static int select_idle_core(struct task_struct
*p
, int core
, struct cpumask
*cpus
, int *idle_cpu
)
6099 if (!static_branch_likely(&sched_smt_present
))
6100 return __select_idle_cpu(core
);
6102 for_each_cpu(cpu
, cpu_smt_mask(core
)) {
6103 if (!available_idle_cpu(cpu
)) {
6105 if (*idle_cpu
== -1) {
6106 if (sched_idle_cpu(cpu
) && cpumask_test_cpu(cpu
, p
->cpus_ptr
)) {
6114 if (*idle_cpu
== -1 && cpumask_test_cpu(cpu
, p
->cpus_ptr
))
6121 cpumask_andnot(cpus
, cpus
, cpu_smt_mask(core
));
6126 * Scan the local SMT mask for idle CPUs.
6128 static int select_idle_smt(struct task_struct
*p
, struct sched_domain
*sd
, int target
)
6132 for_each_cpu(cpu
, cpu_smt_mask(target
)) {
6133 if (!cpumask_test_cpu(cpu
, p
->cpus_ptr
) ||
6134 !cpumask_test_cpu(cpu
, sched_domain_span(sd
)))
6136 if (available_idle_cpu(cpu
) || sched_idle_cpu(cpu
))
6143 #else /* CONFIG_SCHED_SMT */
6145 static inline void set_idle_cores(int cpu
, int val
)
6149 static inline bool test_idle_cores(int cpu
, bool def
)
6154 static inline int select_idle_core(struct task_struct
*p
, int core
, struct cpumask
*cpus
, int *idle_cpu
)
6156 return __select_idle_cpu(core
);
6159 static inline int select_idle_smt(struct task_struct
*p
, struct sched_domain
*sd
, int target
)
6164 #endif /* CONFIG_SCHED_SMT */
6167 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
6168 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
6169 * average idle time for this rq (as found in rq->avg_idle).
6171 static int select_idle_cpu(struct task_struct
*p
, struct sched_domain
*sd
, bool has_idle_core
, int target
)
6173 struct cpumask
*cpus
= this_cpu_cpumask_var_ptr(select_idle_mask
);
6174 int i
, cpu
, idle_cpu
= -1, nr
= INT_MAX
;
6175 int this = smp_processor_id();
6176 struct sched_domain
*this_sd
;
6179 this_sd
= rcu_dereference(*this_cpu_ptr(&sd_llc
));
6183 cpumask_and(cpus
, sched_domain_span(sd
), p
->cpus_ptr
);
6185 if (sched_feat(SIS_PROP
) && !has_idle_core
) {
6186 u64 avg_cost
, avg_idle
, span_avg
;
6189 * Due to large variance we need a large fuzz factor;
6190 * hackbench in particularly is sensitive here.
6192 avg_idle
= this_rq()->avg_idle
/ 512;
6193 avg_cost
= this_sd
->avg_scan_cost
+ 1;
6195 span_avg
= sd
->span_weight
* avg_idle
;
6196 if (span_avg
> 4*avg_cost
)
6197 nr
= div_u64(span_avg
, avg_cost
);
6201 time
= cpu_clock(this);
6204 for_each_cpu_wrap(cpu
, cpus
, target
) {
6205 if (has_idle_core
) {
6206 i
= select_idle_core(p
, cpu
, cpus
, &idle_cpu
);
6207 if ((unsigned int)i
< nr_cpumask_bits
)
6213 idle_cpu
= __select_idle_cpu(cpu
);
6214 if ((unsigned int)idle_cpu
< nr_cpumask_bits
)
6220 set_idle_cores(this, false);
6222 if (sched_feat(SIS_PROP
) && !has_idle_core
) {
6223 time
= cpu_clock(this) - time
;
6224 update_avg(&this_sd
->avg_scan_cost
, time
);
6231 * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
6232 * the task fits. If no CPU is big enough, but there are idle ones, try to
6233 * maximize capacity.
6236 select_idle_capacity(struct task_struct
*p
, struct sched_domain
*sd
, int target
)
6238 unsigned long task_util
, best_cap
= 0;
6239 int cpu
, best_cpu
= -1;
6240 struct cpumask
*cpus
;
6242 cpus
= this_cpu_cpumask_var_ptr(select_idle_mask
);
6243 cpumask_and(cpus
, sched_domain_span(sd
), p
->cpus_ptr
);
6245 task_util
= uclamp_task_util(p
);
6247 for_each_cpu_wrap(cpu
, cpus
, target
) {
6248 unsigned long cpu_cap
= capacity_of(cpu
);
6250 if (!available_idle_cpu(cpu
) && !sched_idle_cpu(cpu
))
6252 if (fits_capacity(task_util
, cpu_cap
))
6255 if (cpu_cap
> best_cap
) {
6264 static inline bool asym_fits_capacity(int task_util
, int cpu
)
6266 if (static_branch_unlikely(&sched_asym_cpucapacity
))
6267 return fits_capacity(task_util
, capacity_of(cpu
));
6273 * Try and locate an idle core/thread in the LLC cache domain.
6275 static int select_idle_sibling(struct task_struct
*p
, int prev
, int target
)
6277 bool has_idle_core
= false;
6278 struct sched_domain
*sd
;
6279 unsigned long task_util
;
6280 int i
, recent_used_cpu
;
6283 * On asymmetric system, update task utilization because we will check
6284 * that the task fits with cpu's capacity.
6286 if (static_branch_unlikely(&sched_asym_cpucapacity
)) {
6287 sync_entity_load_avg(&p
->se
);
6288 task_util
= uclamp_task_util(p
);
6291 if ((available_idle_cpu(target
) || sched_idle_cpu(target
)) &&
6292 asym_fits_capacity(task_util
, target
))
6296 * If the previous CPU is cache affine and idle, don't be stupid:
6298 if (prev
!= target
&& cpus_share_cache(prev
, target
) &&
6299 (available_idle_cpu(prev
) || sched_idle_cpu(prev
)) &&
6300 asym_fits_capacity(task_util
, prev
))
6304 * Allow a per-cpu kthread to stack with the wakee if the
6305 * kworker thread and the tasks previous CPUs are the same.
6306 * The assumption is that the wakee queued work for the
6307 * per-cpu kthread that is now complete and the wakeup is
6308 * essentially a sync wakeup. An obvious example of this
6309 * pattern is IO completions.
6311 if (is_per_cpu_kthread(current
) &&
6312 prev
== smp_processor_id() &&
6313 this_rq()->nr_running
<= 1) {
6317 /* Check a recently used CPU as a potential idle candidate: */
6318 recent_used_cpu
= p
->recent_used_cpu
;
6319 if (recent_used_cpu
!= prev
&&
6320 recent_used_cpu
!= target
&&
6321 cpus_share_cache(recent_used_cpu
, target
) &&
6322 (available_idle_cpu(recent_used_cpu
) || sched_idle_cpu(recent_used_cpu
)) &&
6323 cpumask_test_cpu(p
->recent_used_cpu
, p
->cpus_ptr
) &&
6324 asym_fits_capacity(task_util
, recent_used_cpu
)) {
6326 * Replace recent_used_cpu with prev as it is a potential
6327 * candidate for the next wake:
6329 p
->recent_used_cpu
= prev
;
6330 return recent_used_cpu
;
6334 * For asymmetric CPU capacity systems, our domain of interest is
6335 * sd_asym_cpucapacity rather than sd_llc.
6337 if (static_branch_unlikely(&sched_asym_cpucapacity
)) {
6338 sd
= rcu_dereference(per_cpu(sd_asym_cpucapacity
, target
));
6340 * On an asymmetric CPU capacity system where an exclusive
6341 * cpuset defines a symmetric island (i.e. one unique
6342 * capacity_orig value through the cpuset), the key will be set
6343 * but the CPUs within that cpuset will not have a domain with
6344 * SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
6348 i
= select_idle_capacity(p
, sd
, target
);
6349 return ((unsigned)i
< nr_cpumask_bits
) ? i
: target
;
6353 sd
= rcu_dereference(per_cpu(sd_llc
, target
));
6357 if (sched_smt_active()) {
6358 has_idle_core
= test_idle_cores(target
, false);
6360 if (!has_idle_core
&& cpus_share_cache(prev
, target
)) {
6361 i
= select_idle_smt(p
, sd
, prev
);
6362 if ((unsigned int)i
< nr_cpumask_bits
)
6367 i
= select_idle_cpu(p
, sd
, has_idle_core
, target
);
6368 if ((unsigned)i
< nr_cpumask_bits
)
6375 * cpu_util - Estimates the amount of capacity of a CPU used by CFS tasks.
6376 * @cpu: the CPU to get the utilization of
6378 * The unit of the return value must be the one of capacity so we can compare
6379 * the utilization with the capacity of the CPU that is available for CFS task
6380 * (ie cpu_capacity).
6382 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
6383 * recent utilization of currently non-runnable tasks on a CPU. It represents
6384 * the amount of utilization of a CPU in the range [0..capacity_orig] where
6385 * capacity_orig is the cpu_capacity available at the highest frequency
6386 * (arch_scale_freq_capacity()).
6387 * The utilization of a CPU converges towards a sum equal to or less than the
6388 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
6389 * the running time on this CPU scaled by capacity_curr.
6391 * The estimated utilization of a CPU is defined to be the maximum between its
6392 * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
6393 * currently RUNNABLE on that CPU.
6394 * This allows to properly represent the expected utilization of a CPU which
6395 * has just got a big task running since a long sleep period. At the same time
6396 * however it preserves the benefits of the "blocked utilization" in
6397 * describing the potential for other tasks waking up on the same CPU.
6399 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
6400 * higher than capacity_orig because of unfortunate rounding in
6401 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
6402 * the average stabilizes with the new running time. We need to check that the
6403 * utilization stays within the range of [0..capacity_orig] and cap it if
6404 * necessary. Without utilization capping, a group could be seen as overloaded
6405 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
6406 * available capacity. We allow utilization to overshoot capacity_curr (but not
6407 * capacity_orig) as it useful for predicting the capacity required after task
6408 * migrations (scheduler-driven DVFS).
6410 * Return: the (estimated) utilization for the specified CPU
6412 static inline unsigned long cpu_util(int cpu
)
6414 struct cfs_rq
*cfs_rq
;
6417 cfs_rq
= &cpu_rq(cpu
)->cfs
;
6418 util
= READ_ONCE(cfs_rq
->avg
.util_avg
);
6420 if (sched_feat(UTIL_EST
))
6421 util
= max(util
, READ_ONCE(cfs_rq
->avg
.util_est
.enqueued
));
6423 return min_t(unsigned long, util
, capacity_orig_of(cpu
));
6427 * cpu_util_without: compute cpu utilization without any contributions from *p
6428 * @cpu: the CPU which utilization is requested
6429 * @p: the task which utilization should be discounted
6431 * The utilization of a CPU is defined by the utilization of tasks currently
6432 * enqueued on that CPU as well as tasks which are currently sleeping after an
6433 * execution on that CPU.
6435 * This method returns the utilization of the specified CPU by discounting the
6436 * utilization of the specified task, whenever the task is currently
6437 * contributing to the CPU utilization.
6439 static unsigned long cpu_util_without(int cpu
, struct task_struct
*p
)
6441 struct cfs_rq
*cfs_rq
;
6444 /* Task has no contribution or is new */
6445 if (cpu
!= task_cpu(p
) || !READ_ONCE(p
->se
.avg
.last_update_time
))
6446 return cpu_util(cpu
);
6448 cfs_rq
= &cpu_rq(cpu
)->cfs
;
6449 util
= READ_ONCE(cfs_rq
->avg
.util_avg
);
6451 /* Discount task's util from CPU's util */
6452 lsub_positive(&util
, task_util(p
));
6457 * a) if *p is the only task sleeping on this CPU, then:
6458 * cpu_util (== task_util) > util_est (== 0)
6459 * and thus we return:
6460 * cpu_util_without = (cpu_util - task_util) = 0
6462 * b) if other tasks are SLEEPING on this CPU, which is now exiting
6464 * cpu_util >= task_util
6465 * cpu_util > util_est (== 0)
6466 * and thus we discount *p's blocked utilization to return:
6467 * cpu_util_without = (cpu_util - task_util) >= 0
6469 * c) if other tasks are RUNNABLE on that CPU and
6470 * util_est > cpu_util
6471 * then we use util_est since it returns a more restrictive
6472 * estimation of the spare capacity on that CPU, by just
6473 * considering the expected utilization of tasks already
6474 * runnable on that CPU.
6476 * Cases a) and b) are covered by the above code, while case c) is
6477 * covered by the following code when estimated utilization is
6480 if (sched_feat(UTIL_EST
)) {
6481 unsigned int estimated
=
6482 READ_ONCE(cfs_rq
->avg
.util_est
.enqueued
);
6485 * Despite the following checks we still have a small window
6486 * for a possible race, when an execl's select_task_rq_fair()
6487 * races with LB's detach_task():
6490 * p->on_rq = TASK_ON_RQ_MIGRATING;
6491 * ---------------------------------- A
6492 * deactivate_task() \
6493 * dequeue_task() + RaceTime
6494 * util_est_dequeue() /
6495 * ---------------------------------- B
6497 * The additional check on "current == p" it's required to
6498 * properly fix the execl regression and it helps in further
6499 * reducing the chances for the above race.
6501 if (unlikely(task_on_rq_queued(p
) || current
== p
))
6502 lsub_positive(&estimated
, _task_util_est(p
));
6504 util
= max(util
, estimated
);
6508 * Utilization (estimated) can exceed the CPU capacity, thus let's
6509 * clamp to the maximum CPU capacity to ensure consistency with
6510 * the cpu_util call.
6512 return min_t(unsigned long, util
, capacity_orig_of(cpu
));
6516 * Predicts what cpu_util(@cpu) would return if @p was migrated (and enqueued)
6519 static unsigned long cpu_util_next(int cpu
, struct task_struct
*p
, int dst_cpu
)
6521 struct cfs_rq
*cfs_rq
= &cpu_rq(cpu
)->cfs
;
6522 unsigned long util_est
, util
= READ_ONCE(cfs_rq
->avg
.util_avg
);
6525 * If @p migrates from @cpu to another, remove its contribution. Or,
6526 * if @p migrates from another CPU to @cpu, add its contribution. In
6527 * the other cases, @cpu is not impacted by the migration, so the
6528 * util_avg should already be correct.
6530 if (task_cpu(p
) == cpu
&& dst_cpu
!= cpu
)
6531 lsub_positive(&util
, task_util(p
));
6532 else if (task_cpu(p
) != cpu
&& dst_cpu
== cpu
)
6533 util
+= task_util(p
);
6535 if (sched_feat(UTIL_EST
)) {
6536 util_est
= READ_ONCE(cfs_rq
->avg
.util_est
.enqueued
);
6539 * During wake-up, the task isn't enqueued yet and doesn't
6540 * appear in the cfs_rq->avg.util_est.enqueued of any rq,
6541 * so just add it (if needed) to "simulate" what will be
6542 * cpu_util() after the task has been enqueued.
6545 util_est
+= _task_util_est(p
);
6547 util
= max(util
, util_est
);
6550 return min(util
, capacity_orig_of(cpu
));
6554 * compute_energy(): Estimates the energy that @pd would consume if @p was
6555 * migrated to @dst_cpu. compute_energy() predicts what will be the utilization
6556 * landscape of @pd's CPUs after the task migration, and uses the Energy Model
6557 * to compute what would be the energy if we decided to actually migrate that
6561 compute_energy(struct task_struct
*p
, int dst_cpu
, struct perf_domain
*pd
)
6563 struct cpumask
*pd_mask
= perf_domain_span(pd
);
6564 unsigned long cpu_cap
= arch_scale_cpu_capacity(cpumask_first(pd_mask
));
6565 unsigned long max_util
= 0, sum_util
= 0;
6569 * The capacity state of CPUs of the current rd can be driven by CPUs
6570 * of another rd if they belong to the same pd. So, account for the
6571 * utilization of these CPUs too by masking pd with cpu_online_mask
6572 * instead of the rd span.
6574 * If an entire pd is outside of the current rd, it will not appear in
6575 * its pd list and will not be accounted by compute_energy().
6577 for_each_cpu_and(cpu
, pd_mask
, cpu_online_mask
) {
6578 unsigned long util_freq
= cpu_util_next(cpu
, p
, dst_cpu
);
6579 unsigned long cpu_util
, util_running
= util_freq
;
6580 struct task_struct
*tsk
= NULL
;
6583 * When @p is placed on @cpu:
6585 * util_running = max(cpu_util, cpu_util_est) +
6586 * max(task_util, _task_util_est)
6588 * while cpu_util_next is: max(cpu_util + task_util,
6589 * cpu_util_est + _task_util_est)
6591 if (cpu
== dst_cpu
) {
6594 cpu_util_next(cpu
, p
, -1) + task_util_est(p
);
6598 * Busy time computation: utilization clamping is not
6599 * required since the ratio (sum_util / cpu_capacity)
6600 * is already enough to scale the EM reported power
6601 * consumption at the (eventually clamped) cpu_capacity.
6603 sum_util
+= effective_cpu_util(cpu
, util_running
, cpu_cap
,
6607 * Performance domain frequency: utilization clamping
6608 * must be considered since it affects the selection
6609 * of the performance domain frequency.
6610 * NOTE: in case RT tasks are running, by default the
6611 * FREQUENCY_UTIL's utilization can be max OPP.
6613 cpu_util
= effective_cpu_util(cpu
, util_freq
, cpu_cap
,
6614 FREQUENCY_UTIL
, tsk
);
6615 max_util
= max(max_util
, cpu_util
);
6618 return em_cpu_energy(pd
->em_pd
, max_util
, sum_util
);
6622 * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
6623 * waking task. find_energy_efficient_cpu() looks for the CPU with maximum
6624 * spare capacity in each performance domain and uses it as a potential
6625 * candidate to execute the task. Then, it uses the Energy Model to figure
6626 * out which of the CPU candidates is the most energy-efficient.
6628 * The rationale for this heuristic is as follows. In a performance domain,
6629 * all the most energy efficient CPU candidates (according to the Energy
6630 * Model) are those for which we'll request a low frequency. When there are
6631 * several CPUs for which the frequency request will be the same, we don't
6632 * have enough data to break the tie between them, because the Energy Model
6633 * only includes active power costs. With this model, if we assume that
6634 * frequency requests follow utilization (e.g. using schedutil), the CPU with
6635 * the maximum spare capacity in a performance domain is guaranteed to be among
6636 * the best candidates of the performance domain.
6638 * In practice, it could be preferable from an energy standpoint to pack
6639 * small tasks on a CPU in order to let other CPUs go in deeper idle states,
6640 * but that could also hurt our chances to go cluster idle, and we have no
6641 * ways to tell with the current Energy Model if this is actually a good
6642 * idea or not. So, find_energy_efficient_cpu() basically favors
6643 * cluster-packing, and spreading inside a cluster. That should at least be
6644 * a good thing for latency, and this is consistent with the idea that most
6645 * of the energy savings of EAS come from the asymmetry of the system, and
6646 * not so much from breaking the tie between identical CPUs. That's also the
6647 * reason why EAS is enabled in the topology code only for systems where
6648 * SD_ASYM_CPUCAPACITY is set.
6650 * NOTE: Forkees are not accepted in the energy-aware wake-up path because
6651 * they don't have any useful utilization data yet and it's not possible to
6652 * forecast their impact on energy consumption. Consequently, they will be
6653 * placed by find_idlest_cpu() on the least loaded CPU, which might turn out
6654 * to be energy-inefficient in some use-cases. The alternative would be to
6655 * bias new tasks towards specific types of CPUs first, or to try to infer
6656 * their util_avg from the parent task, but those heuristics could hurt
6657 * other use-cases too. So, until someone finds a better way to solve this,
6658 * let's keep things simple by re-using the existing slow path.
6660 static int find_energy_efficient_cpu(struct task_struct
*p
, int prev_cpu
)
6662 unsigned long prev_delta
= ULONG_MAX
, best_delta
= ULONG_MAX
;
6663 struct root_domain
*rd
= cpu_rq(smp_processor_id())->rd
;
6664 unsigned long cpu_cap
, util
, base_energy
= 0;
6665 int cpu
, best_energy_cpu
= prev_cpu
;
6666 struct sched_domain
*sd
;
6667 struct perf_domain
*pd
;
6670 pd
= rcu_dereference(rd
->pd
);
6671 if (!pd
|| READ_ONCE(rd
->overutilized
))
6675 * Energy-aware wake-up happens on the lowest sched_domain starting
6676 * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
6678 sd
= rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity
));
6679 while (sd
&& !cpumask_test_cpu(prev_cpu
, sched_domain_span(sd
)))
6684 sync_entity_load_avg(&p
->se
);
6685 if (!task_util_est(p
))
6688 for (; pd
; pd
= pd
->next
) {
6689 unsigned long cur_delta
, spare_cap
, max_spare_cap
= 0;
6690 unsigned long base_energy_pd
;
6691 int max_spare_cap_cpu
= -1;
6693 /* Compute the 'base' energy of the pd, without @p */
6694 base_energy_pd
= compute_energy(p
, -1, pd
);
6695 base_energy
+= base_energy_pd
;
6697 for_each_cpu_and(cpu
, perf_domain_span(pd
), sched_domain_span(sd
)) {
6698 if (!cpumask_test_cpu(cpu
, p
->cpus_ptr
))
6701 util
= cpu_util_next(cpu
, p
, cpu
);
6702 cpu_cap
= capacity_of(cpu
);
6703 spare_cap
= cpu_cap
;
6704 lsub_positive(&spare_cap
, util
);
6707 * Skip CPUs that cannot satisfy the capacity request.
6708 * IOW, placing the task there would make the CPU
6709 * overutilized. Take uclamp into account to see how
6710 * much capacity we can get out of the CPU; this is
6711 * aligned with sched_cpu_util().
6713 util
= uclamp_rq_util_with(cpu_rq(cpu
), util
, p
);
6714 if (!fits_capacity(util
, cpu_cap
))
6717 /* Always use prev_cpu as a candidate. */
6718 if (cpu
== prev_cpu
) {
6719 prev_delta
= compute_energy(p
, prev_cpu
, pd
);
6720 prev_delta
-= base_energy_pd
;
6721 best_delta
= min(best_delta
, prev_delta
);
6725 * Find the CPU with the maximum spare capacity in
6726 * the performance domain
6728 if (spare_cap
> max_spare_cap
) {
6729 max_spare_cap
= spare_cap
;
6730 max_spare_cap_cpu
= cpu
;
6734 /* Evaluate the energy impact of using this CPU. */
6735 if (max_spare_cap_cpu
>= 0 && max_spare_cap_cpu
!= prev_cpu
) {
6736 cur_delta
= compute_energy(p
, max_spare_cap_cpu
, pd
);
6737 cur_delta
-= base_energy_pd
;
6738 if (cur_delta
< best_delta
) {
6739 best_delta
= cur_delta
;
6740 best_energy_cpu
= max_spare_cap_cpu
;
6748 * Pick the best CPU if prev_cpu cannot be used, or if it saves at
6749 * least 6% of the energy used by prev_cpu.
6751 if (prev_delta
== ULONG_MAX
)
6752 return best_energy_cpu
;
6754 if ((prev_delta
- best_delta
) > ((prev_delta
+ base_energy
) >> 4))
6755 return best_energy_cpu
;
6766 * select_task_rq_fair: Select target runqueue for the waking task in domains
6767 * that have the relevant SD flag set. In practice, this is SD_BALANCE_WAKE,
6768 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
6770 * Balances load by selecting the idlest CPU in the idlest group, or under
6771 * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
6773 * Returns the target CPU number.
6775 * preempt must be disabled.
6778 select_task_rq_fair(struct task_struct
*p
, int prev_cpu
, int wake_flags
)
6780 int sync
= (wake_flags
& WF_SYNC
) && !(current
->flags
& PF_EXITING
);
6781 struct sched_domain
*tmp
, *sd
= NULL
;
6782 int cpu
= smp_processor_id();
6783 int new_cpu
= prev_cpu
;
6784 int want_affine
= 0;
6785 /* SD_flags and WF_flags share the first nibble */
6786 int sd_flag
= wake_flags
& 0xF;
6788 if (wake_flags
& WF_TTWU
) {
6791 if (sched_energy_enabled()) {
6792 new_cpu
= find_energy_efficient_cpu(p
, prev_cpu
);
6798 want_affine
= !wake_wide(p
) && cpumask_test_cpu(cpu
, p
->cpus_ptr
);
6802 for_each_domain(cpu
, tmp
) {
6804 * If both 'cpu' and 'prev_cpu' are part of this domain,
6805 * cpu is a valid SD_WAKE_AFFINE target.
6807 if (want_affine
&& (tmp
->flags
& SD_WAKE_AFFINE
) &&
6808 cpumask_test_cpu(prev_cpu
, sched_domain_span(tmp
))) {
6809 if (cpu
!= prev_cpu
)
6810 new_cpu
= wake_affine(tmp
, p
, cpu
, prev_cpu
, sync
);
6812 sd
= NULL
; /* Prefer wake_affine over balance flags */
6816 if (tmp
->flags
& sd_flag
)
6818 else if (!want_affine
)
6824 new_cpu
= find_idlest_cpu(sd
, p
, cpu
, prev_cpu
, sd_flag
);
6825 } else if (wake_flags
& WF_TTWU
) { /* XXX always ? */
6827 new_cpu
= select_idle_sibling(p
, prev_cpu
, new_cpu
);
6830 current
->recent_used_cpu
= cpu
;
6837 static void detach_entity_cfs_rq(struct sched_entity
*se
);
6840 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6841 * cfs_rq_of(p) references at time of call are still valid and identify the
6842 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6844 static void migrate_task_rq_fair(struct task_struct
*p
, int new_cpu
)
6847 * As blocked tasks retain absolute vruntime the migration needs to
6848 * deal with this by subtracting the old and adding the new
6849 * min_vruntime -- the latter is done by enqueue_entity() when placing
6850 * the task on the new runqueue.
6852 if (p
->state
== TASK_WAKING
) {
6853 struct sched_entity
*se
= &p
->se
;
6854 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
6857 #ifndef CONFIG_64BIT
6858 u64 min_vruntime_copy
;
6861 min_vruntime_copy
= cfs_rq
->min_vruntime_copy
;
6863 min_vruntime
= cfs_rq
->min_vruntime
;
6864 } while (min_vruntime
!= min_vruntime_copy
);
6866 min_vruntime
= cfs_rq
->min_vruntime
;
6869 se
->vruntime
-= min_vruntime
;
6872 if (p
->on_rq
== TASK_ON_RQ_MIGRATING
) {
6874 * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
6875 * rq->lock and can modify state directly.
6877 lockdep_assert_held(&task_rq(p
)->lock
);
6878 detach_entity_cfs_rq(&p
->se
);
6882 * We are supposed to update the task to "current" time, then
6883 * its up to date and ready to go to new CPU/cfs_rq. But we
6884 * have difficulty in getting what current time is, so simply
6885 * throw away the out-of-date time. This will result in the
6886 * wakee task is less decayed, but giving the wakee more load
6889 remove_entity_load_avg(&p
->se
);
6892 /* Tell new CPU we are migrated */
6893 p
->se
.avg
.last_update_time
= 0;
6895 /* We have migrated, no longer consider this task hot */
6896 p
->se
.exec_start
= 0;
6898 update_scan_period(p
, new_cpu
);
6901 static void task_dead_fair(struct task_struct
*p
)
6903 remove_entity_load_avg(&p
->se
);
6907 balance_fair(struct rq
*rq
, struct task_struct
*prev
, struct rq_flags
*rf
)
6912 return newidle_balance(rq
, rf
) != 0;
6914 #endif /* CONFIG_SMP */
6916 static unsigned long wakeup_gran(struct sched_entity
*se
)
6918 unsigned long gran
= sysctl_sched_wakeup_granularity
;
6921 * Since its curr running now, convert the gran from real-time
6922 * to virtual-time in his units.
6924 * By using 'se' instead of 'curr' we penalize light tasks, so
6925 * they get preempted easier. That is, if 'se' < 'curr' then
6926 * the resulting gran will be larger, therefore penalizing the
6927 * lighter, if otoh 'se' > 'curr' then the resulting gran will
6928 * be smaller, again penalizing the lighter task.
6930 * This is especially important for buddies when the leftmost
6931 * task is higher priority than the buddy.
6933 return calc_delta_fair(gran
, se
);
6937 * Should 'se' preempt 'curr'.
6951 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
)
6953 s64 gran
, vdiff
= curr
->vruntime
- se
->vruntime
;
6958 gran
= wakeup_gran(se
);
6965 static void set_last_buddy(struct sched_entity
*se
)
6967 if (entity_is_task(se
) && unlikely(task_has_idle_policy(task_of(se
))))
6970 for_each_sched_entity(se
) {
6971 if (SCHED_WARN_ON(!se
->on_rq
))
6973 cfs_rq_of(se
)->last
= se
;
6977 static void set_next_buddy(struct sched_entity
*se
)
6979 if (entity_is_task(se
) && unlikely(task_has_idle_policy(task_of(se
))))
6982 for_each_sched_entity(se
) {
6983 if (SCHED_WARN_ON(!se
->on_rq
))
6985 cfs_rq_of(se
)->next
= se
;
6989 static void set_skip_buddy(struct sched_entity
*se
)
6991 for_each_sched_entity(se
)
6992 cfs_rq_of(se
)->skip
= se
;
6996 * Preempt the current task with a newly woken task if needed:
6998 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
)
7000 struct task_struct
*curr
= rq
->curr
;
7001 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
7002 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
7003 int scale
= cfs_rq
->nr_running
>= sched_nr_latency
;
7004 int next_buddy_marked
= 0;
7006 if (unlikely(se
== pse
))
7010 * This is possible from callers such as attach_tasks(), in which we
7011 * unconditionally check_preempt_curr() after an enqueue (which may have
7012 * lead to a throttle). This both saves work and prevents false
7013 * next-buddy nomination below.
7015 if (unlikely(throttled_hierarchy(cfs_rq_of(pse
))))
7018 if (sched_feat(NEXT_BUDDY
) && scale
&& !(wake_flags
& WF_FORK
)) {
7019 set_next_buddy(pse
);
7020 next_buddy_marked
= 1;
7024 * We can come here with TIF_NEED_RESCHED already set from new task
7027 * Note: this also catches the edge-case of curr being in a throttled
7028 * group (e.g. via set_curr_task), since update_curr() (in the
7029 * enqueue of curr) will have resulted in resched being set. This
7030 * prevents us from potentially nominating it as a false LAST_BUDDY
7033 if (test_tsk_need_resched(curr
))
7036 /* Idle tasks are by definition preempted by non-idle tasks. */
7037 if (unlikely(task_has_idle_policy(curr
)) &&
7038 likely(!task_has_idle_policy(p
)))
7042 * Batch and idle tasks do not preempt non-idle tasks (their preemption
7043 * is driven by the tick):
7045 if (unlikely(p
->policy
!= SCHED_NORMAL
) || !sched_feat(WAKEUP_PREEMPTION
))
7048 find_matching_se(&se
, &pse
);
7049 update_curr(cfs_rq_of(se
));
7051 if (wakeup_preempt_entity(se
, pse
) == 1) {
7053 * Bias pick_next to pick the sched entity that is
7054 * triggering this preemption.
7056 if (!next_buddy_marked
)
7057 set_next_buddy(pse
);
7066 * Only set the backward buddy when the current task is still
7067 * on the rq. This can happen when a wakeup gets interleaved
7068 * with schedule on the ->pre_schedule() or idle_balance()
7069 * point, either of which can * drop the rq lock.
7071 * Also, during early boot the idle thread is in the fair class,
7072 * for obvious reasons its a bad idea to schedule back to it.
7074 if (unlikely(!se
->on_rq
|| curr
== rq
->idle
))
7077 if (sched_feat(LAST_BUDDY
) && scale
&& entity_is_task(se
))
7081 struct task_struct
*
7082 pick_next_task_fair(struct rq
*rq
, struct task_struct
*prev
, struct rq_flags
*rf
)
7084 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
7085 struct sched_entity
*se
;
7086 struct task_struct
*p
;
7090 if (!sched_fair_runnable(rq
))
7093 #ifdef CONFIG_FAIR_GROUP_SCHED
7094 if (!prev
|| prev
->sched_class
!= &fair_sched_class
)
7098 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
7099 * likely that a next task is from the same cgroup as the current.
7101 * Therefore attempt to avoid putting and setting the entire cgroup
7102 * hierarchy, only change the part that actually changes.
7106 struct sched_entity
*curr
= cfs_rq
->curr
;
7109 * Since we got here without doing put_prev_entity() we also
7110 * have to consider cfs_rq->curr. If it is still a runnable
7111 * entity, update_curr() will update its vruntime, otherwise
7112 * forget we've ever seen it.
7116 update_curr(cfs_rq
);
7121 * This call to check_cfs_rq_runtime() will do the
7122 * throttle and dequeue its entity in the parent(s).
7123 * Therefore the nr_running test will indeed
7126 if (unlikely(check_cfs_rq_runtime(cfs_rq
))) {
7129 if (!cfs_rq
->nr_running
)
7136 se
= pick_next_entity(cfs_rq
, curr
);
7137 cfs_rq
= group_cfs_rq(se
);
7143 * Since we haven't yet done put_prev_entity and if the selected task
7144 * is a different task than we started out with, try and touch the
7145 * least amount of cfs_rqs.
7148 struct sched_entity
*pse
= &prev
->se
;
7150 while (!(cfs_rq
= is_same_group(se
, pse
))) {
7151 int se_depth
= se
->depth
;
7152 int pse_depth
= pse
->depth
;
7154 if (se_depth
<= pse_depth
) {
7155 put_prev_entity(cfs_rq_of(pse
), pse
);
7156 pse
= parent_entity(pse
);
7158 if (se_depth
>= pse_depth
) {
7159 set_next_entity(cfs_rq_of(se
), se
);
7160 se
= parent_entity(se
);
7164 put_prev_entity(cfs_rq
, pse
);
7165 set_next_entity(cfs_rq
, se
);
7172 put_prev_task(rq
, prev
);
7175 se
= pick_next_entity(cfs_rq
, NULL
);
7176 set_next_entity(cfs_rq
, se
);
7177 cfs_rq
= group_cfs_rq(se
);
7182 done
: __maybe_unused
;
7185 * Move the next running task to the front of
7186 * the list, so our cfs_tasks list becomes MRU
7189 list_move(&p
->se
.group_node
, &rq
->cfs_tasks
);
7192 if (hrtick_enabled_fair(rq
))
7193 hrtick_start_fair(rq
, p
);
7195 update_misfit_status(p
, rq
);
7203 new_tasks
= newidle_balance(rq
, rf
);
7206 * Because newidle_balance() releases (and re-acquires) rq->lock, it is
7207 * possible for any higher priority task to appear. In that case we
7208 * must re-start the pick_next_entity() loop.
7217 * rq is about to be idle, check if we need to update the
7218 * lost_idle_time of clock_pelt
7220 update_idle_rq_clock_pelt(rq
);
7225 static struct task_struct
*__pick_next_task_fair(struct rq
*rq
)
7227 return pick_next_task_fair(rq
, NULL
, NULL
);
7231 * Account for a descheduled task:
7233 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
7235 struct sched_entity
*se
= &prev
->se
;
7236 struct cfs_rq
*cfs_rq
;
7238 for_each_sched_entity(se
) {
7239 cfs_rq
= cfs_rq_of(se
);
7240 put_prev_entity(cfs_rq
, se
);
7245 * sched_yield() is very simple
7247 * The magic of dealing with the ->skip buddy is in pick_next_entity.
7249 static void yield_task_fair(struct rq
*rq
)
7251 struct task_struct
*curr
= rq
->curr
;
7252 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
7253 struct sched_entity
*se
= &curr
->se
;
7256 * Are we the only task in the tree?
7258 if (unlikely(rq
->nr_running
== 1))
7261 clear_buddies(cfs_rq
, se
);
7263 if (curr
->policy
!= SCHED_BATCH
) {
7264 update_rq_clock(rq
);
7266 * Update run-time statistics of the 'current'.
7268 update_curr(cfs_rq
);
7270 * Tell update_rq_clock() that we've just updated,
7271 * so we don't do microscopic update in schedule()
7272 * and double the fastpath cost.
7274 rq_clock_skip_update(rq
);
7280 static bool yield_to_task_fair(struct rq
*rq
, struct task_struct
*p
)
7282 struct sched_entity
*se
= &p
->se
;
7284 /* throttled hierarchies are not runnable */
7285 if (!se
->on_rq
|| throttled_hierarchy(cfs_rq_of(se
)))
7288 /* Tell the scheduler that we'd really like pse to run next. */
7291 yield_task_fair(rq
);
7297 /**************************************************
7298 * Fair scheduling class load-balancing methods.
7302 * The purpose of load-balancing is to achieve the same basic fairness the
7303 * per-CPU scheduler provides, namely provide a proportional amount of compute
7304 * time to each task. This is expressed in the following equation:
7306 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
7308 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
7309 * W_i,0 is defined as:
7311 * W_i,0 = \Sum_j w_i,j (2)
7313 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
7314 * is derived from the nice value as per sched_prio_to_weight[].
7316 * The weight average is an exponential decay average of the instantaneous
7319 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
7321 * C_i is the compute capacity of CPU i, typically it is the
7322 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
7323 * can also include other factors [XXX].
7325 * To achieve this balance we define a measure of imbalance which follows
7326 * directly from (1):
7328 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
7330 * We them move tasks around to minimize the imbalance. In the continuous
7331 * function space it is obvious this converges, in the discrete case we get
7332 * a few fun cases generally called infeasible weight scenarios.
7335 * - infeasible weights;
7336 * - local vs global optima in the discrete case. ]
7341 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
7342 * for all i,j solution, we create a tree of CPUs that follows the hardware
7343 * topology where each level pairs two lower groups (or better). This results
7344 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
7345 * tree to only the first of the previous level and we decrease the frequency
7346 * of load-balance at each level inv. proportional to the number of CPUs in
7352 * \Sum { --- * --- * 2^i } = O(n) (5)
7354 * `- size of each group
7355 * | | `- number of CPUs doing load-balance
7357 * `- sum over all levels
7359 * Coupled with a limit on how many tasks we can migrate every balance pass,
7360 * this makes (5) the runtime complexity of the balancer.
7362 * An important property here is that each CPU is still (indirectly) connected
7363 * to every other CPU in at most O(log n) steps:
7365 * The adjacency matrix of the resulting graph is given by:
7368 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
7371 * And you'll find that:
7373 * A^(log_2 n)_i,j != 0 for all i,j (7)
7375 * Showing there's indeed a path between every CPU in at most O(log n) steps.
7376 * The task movement gives a factor of O(m), giving a convergence complexity
7379 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
7384 * In order to avoid CPUs going idle while there's still work to do, new idle
7385 * balancing is more aggressive and has the newly idle CPU iterate up the domain
7386 * tree itself instead of relying on other CPUs to bring it work.
7388 * This adds some complexity to both (5) and (8) but it reduces the total idle
7396 * Cgroups make a horror show out of (2), instead of a simple sum we get:
7399 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
7404 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
7406 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
7408 * The big problem is S_k, its a global sum needed to compute a local (W_i)
7411 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
7412 * rewrite all of this once again.]
7415 static unsigned long __read_mostly max_load_balance_interval
= HZ
/10;
7417 enum fbq_type
{ regular
, remote
, all
};
7420 * 'group_type' describes the group of CPUs at the moment of load balancing.
7422 * The enum is ordered by pulling priority, with the group with lowest priority
7423 * first so the group_type can simply be compared when selecting the busiest
7424 * group. See update_sd_pick_busiest().
7427 /* The group has spare capacity that can be used to run more tasks. */
7428 group_has_spare
= 0,
7430 * The group is fully used and the tasks don't compete for more CPU
7431 * cycles. Nevertheless, some tasks might wait before running.
7435 * SD_ASYM_CPUCAPACITY only: One task doesn't fit with CPU's capacity
7436 * and must be migrated to a more powerful CPU.
7440 * SD_ASYM_PACKING only: One local CPU with higher capacity is available,
7441 * and the task should be migrated to it instead of running on the
7446 * The tasks' affinity constraints previously prevented the scheduler
7447 * from balancing the load across the system.
7451 * The CPU is overloaded and can't provide expected CPU cycles to all
7457 enum migration_type
{
7464 #define LBF_ALL_PINNED 0x01
7465 #define LBF_NEED_BREAK 0x02
7466 #define LBF_DST_PINNED 0x04
7467 #define LBF_SOME_PINNED 0x08
7468 #define LBF_ACTIVE_LB 0x10
7471 struct sched_domain
*sd
;
7479 struct cpumask
*dst_grpmask
;
7481 enum cpu_idle_type idle
;
7483 /* The set of CPUs under consideration for load-balancing */
7484 struct cpumask
*cpus
;
7489 unsigned int loop_break
;
7490 unsigned int loop_max
;
7492 enum fbq_type fbq_type
;
7493 enum migration_type migration_type
;
7494 struct list_head tasks
;
7498 * Is this task likely cache-hot:
7500 static int task_hot(struct task_struct
*p
, struct lb_env
*env
)
7504 lockdep_assert_held(&env
->src_rq
->lock
);
7506 if (p
->sched_class
!= &fair_sched_class
)
7509 if (unlikely(task_has_idle_policy(p
)))
7512 /* SMT siblings share cache */
7513 if (env
->sd
->flags
& SD_SHARE_CPUCAPACITY
)
7517 * Buddy candidates are cache hot:
7519 if (sched_feat(CACHE_HOT_BUDDY
) && env
->dst_rq
->nr_running
&&
7520 (&p
->se
== cfs_rq_of(&p
->se
)->next
||
7521 &p
->se
== cfs_rq_of(&p
->se
)->last
))
7524 if (sysctl_sched_migration_cost
== -1)
7526 if (sysctl_sched_migration_cost
== 0)
7529 delta
= rq_clock_task(env
->src_rq
) - p
->se
.exec_start
;
7531 return delta
< (s64
)sysctl_sched_migration_cost
;
7534 #ifdef CONFIG_NUMA_BALANCING
7536 * Returns 1, if task migration degrades locality
7537 * Returns 0, if task migration improves locality i.e migration preferred.
7538 * Returns -1, if task migration is not affected by locality.
7540 static int migrate_degrades_locality(struct task_struct
*p
, struct lb_env
*env
)
7542 struct numa_group
*numa_group
= rcu_dereference(p
->numa_group
);
7543 unsigned long src_weight
, dst_weight
;
7544 int src_nid
, dst_nid
, dist
;
7546 if (!static_branch_likely(&sched_numa_balancing
))
7549 if (!p
->numa_faults
|| !(env
->sd
->flags
& SD_NUMA
))
7552 src_nid
= cpu_to_node(env
->src_cpu
);
7553 dst_nid
= cpu_to_node(env
->dst_cpu
);
7555 if (src_nid
== dst_nid
)
7558 /* Migrating away from the preferred node is always bad. */
7559 if (src_nid
== p
->numa_preferred_nid
) {
7560 if (env
->src_rq
->nr_running
> env
->src_rq
->nr_preferred_running
)
7566 /* Encourage migration to the preferred node. */
7567 if (dst_nid
== p
->numa_preferred_nid
)
7570 /* Leaving a core idle is often worse than degrading locality. */
7571 if (env
->idle
== CPU_IDLE
)
7574 dist
= node_distance(src_nid
, dst_nid
);
7576 src_weight
= group_weight(p
, src_nid
, dist
);
7577 dst_weight
= group_weight(p
, dst_nid
, dist
);
7579 src_weight
= task_weight(p
, src_nid
, dist
);
7580 dst_weight
= task_weight(p
, dst_nid
, dist
);
7583 return dst_weight
< src_weight
;
7587 static inline int migrate_degrades_locality(struct task_struct
*p
,
7595 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
7598 int can_migrate_task(struct task_struct
*p
, struct lb_env
*env
)
7602 lockdep_assert_held(&env
->src_rq
->lock
);
7605 * We do not migrate tasks that are:
7606 * 1) throttled_lb_pair, or
7607 * 2) cannot be migrated to this CPU due to cpus_ptr, or
7608 * 3) running (obviously), or
7609 * 4) are cache-hot on their current CPU.
7611 if (throttled_lb_pair(task_group(p
), env
->src_cpu
, env
->dst_cpu
))
7614 /* Disregard pcpu kthreads; they are where they need to be. */
7615 if (kthread_is_per_cpu(p
))
7618 if (!cpumask_test_cpu(env
->dst_cpu
, p
->cpus_ptr
)) {
7621 schedstat_inc(p
->se
.statistics
.nr_failed_migrations_affine
);
7623 env
->flags
|= LBF_SOME_PINNED
;
7626 * Remember if this task can be migrated to any other CPU in
7627 * our sched_group. We may want to revisit it if we couldn't
7628 * meet load balance goals by pulling other tasks on src_cpu.
7630 * Avoid computing new_dst_cpu
7632 * - if we have already computed one in current iteration
7633 * - if it's an active balance
7635 if (env
->idle
== CPU_NEWLY_IDLE
||
7636 env
->flags
& (LBF_DST_PINNED
| LBF_ACTIVE_LB
))
7639 /* Prevent to re-select dst_cpu via env's CPUs: */
7640 for_each_cpu_and(cpu
, env
->dst_grpmask
, env
->cpus
) {
7641 if (cpumask_test_cpu(cpu
, p
->cpus_ptr
)) {
7642 env
->flags
|= LBF_DST_PINNED
;
7643 env
->new_dst_cpu
= cpu
;
7651 /* Record that we found at least one task that could run on dst_cpu */
7652 env
->flags
&= ~LBF_ALL_PINNED
;
7654 if (task_running(env
->src_rq
, p
)) {
7655 schedstat_inc(p
->se
.statistics
.nr_failed_migrations_running
);
7660 * Aggressive migration if:
7662 * 2) destination numa is preferred
7663 * 3) task is cache cold, or
7664 * 4) too many balance attempts have failed.
7666 if (env
->flags
& LBF_ACTIVE_LB
)
7669 tsk_cache_hot
= migrate_degrades_locality(p
, env
);
7670 if (tsk_cache_hot
== -1)
7671 tsk_cache_hot
= task_hot(p
, env
);
7673 if (tsk_cache_hot
<= 0 ||
7674 env
->sd
->nr_balance_failed
> env
->sd
->cache_nice_tries
) {
7675 if (tsk_cache_hot
== 1) {
7676 schedstat_inc(env
->sd
->lb_hot_gained
[env
->idle
]);
7677 schedstat_inc(p
->se
.statistics
.nr_forced_migrations
);
7682 schedstat_inc(p
->se
.statistics
.nr_failed_migrations_hot
);
7687 * detach_task() -- detach the task for the migration specified in env
7689 static void detach_task(struct task_struct
*p
, struct lb_env
*env
)
7691 lockdep_assert_held(&env
->src_rq
->lock
);
7693 deactivate_task(env
->src_rq
, p
, DEQUEUE_NOCLOCK
);
7694 set_task_cpu(p
, env
->dst_cpu
);
7698 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7699 * part of active balancing operations within "domain".
7701 * Returns a task if successful and NULL otherwise.
7703 static struct task_struct
*detach_one_task(struct lb_env
*env
)
7705 struct task_struct
*p
;
7707 lockdep_assert_held(&env
->src_rq
->lock
);
7709 list_for_each_entry_reverse(p
,
7710 &env
->src_rq
->cfs_tasks
, se
.group_node
) {
7711 if (!can_migrate_task(p
, env
))
7714 detach_task(p
, env
);
7717 * Right now, this is only the second place where
7718 * lb_gained[env->idle] is updated (other is detach_tasks)
7719 * so we can safely collect stats here rather than
7720 * inside detach_tasks().
7722 schedstat_inc(env
->sd
->lb_gained
[env
->idle
]);
7728 static const unsigned int sched_nr_migrate_break
= 32;
7731 * detach_tasks() -- tries to detach up to imbalance load/util/tasks from
7732 * busiest_rq, as part of a balancing operation within domain "sd".
7734 * Returns number of detached tasks if successful and 0 otherwise.
7736 static int detach_tasks(struct lb_env
*env
)
7738 struct list_head
*tasks
= &env
->src_rq
->cfs_tasks
;
7739 unsigned long util
, load
;
7740 struct task_struct
*p
;
7743 lockdep_assert_held(&env
->src_rq
->lock
);
7746 * Source run queue has been emptied by another CPU, clear
7747 * LBF_ALL_PINNED flag as we will not test any task.
7749 if (env
->src_rq
->nr_running
<= 1) {
7750 env
->flags
&= ~LBF_ALL_PINNED
;
7754 if (env
->imbalance
<= 0)
7757 while (!list_empty(tasks
)) {
7759 * We don't want to steal all, otherwise we may be treated likewise,
7760 * which could at worst lead to a livelock crash.
7762 if (env
->idle
!= CPU_NOT_IDLE
&& env
->src_rq
->nr_running
<= 1)
7765 p
= list_last_entry(tasks
, struct task_struct
, se
.group_node
);
7768 /* We've more or less seen every task there is, call it quits */
7769 if (env
->loop
> env
->loop_max
)
7772 /* take a breather every nr_migrate tasks */
7773 if (env
->loop
> env
->loop_break
) {
7774 env
->loop_break
+= sched_nr_migrate_break
;
7775 env
->flags
|= LBF_NEED_BREAK
;
7779 if (!can_migrate_task(p
, env
))
7782 switch (env
->migration_type
) {
7785 * Depending of the number of CPUs and tasks and the
7786 * cgroup hierarchy, task_h_load() can return a null
7787 * value. Make sure that env->imbalance decreases
7788 * otherwise detach_tasks() will stop only after
7789 * detaching up to loop_max tasks.
7791 load
= max_t(unsigned long, task_h_load(p
), 1);
7793 if (sched_feat(LB_MIN
) &&
7794 load
< 16 && !env
->sd
->nr_balance_failed
)
7798 * Make sure that we don't migrate too much load.
7799 * Nevertheless, let relax the constraint if
7800 * scheduler fails to find a good waiting task to
7803 if (shr_bound(load
, env
->sd
->nr_balance_failed
) > env
->imbalance
)
7806 env
->imbalance
-= load
;
7810 util
= task_util_est(p
);
7812 if (util
> env
->imbalance
)
7815 env
->imbalance
-= util
;
7822 case migrate_misfit
:
7823 /* This is not a misfit task */
7824 if (task_fits_capacity(p
, capacity_of(env
->src_cpu
)))
7831 detach_task(p
, env
);
7832 list_add(&p
->se
.group_node
, &env
->tasks
);
7836 #ifdef CONFIG_PREEMPTION
7838 * NEWIDLE balancing is a source of latency, so preemptible
7839 * kernels will stop after the first task is detached to minimize
7840 * the critical section.
7842 if (env
->idle
== CPU_NEWLY_IDLE
)
7847 * We only want to steal up to the prescribed amount of
7850 if (env
->imbalance
<= 0)
7855 list_move(&p
->se
.group_node
, tasks
);
7859 * Right now, this is one of only two places we collect this stat
7860 * so we can safely collect detach_one_task() stats here rather
7861 * than inside detach_one_task().
7863 schedstat_add(env
->sd
->lb_gained
[env
->idle
], detached
);
7869 * attach_task() -- attach the task detached by detach_task() to its new rq.
7871 static void attach_task(struct rq
*rq
, struct task_struct
*p
)
7873 lockdep_assert_held(&rq
->lock
);
7875 BUG_ON(task_rq(p
) != rq
);
7876 activate_task(rq
, p
, ENQUEUE_NOCLOCK
);
7877 check_preempt_curr(rq
, p
, 0);
7881 * attach_one_task() -- attaches the task returned from detach_one_task() to
7884 static void attach_one_task(struct rq
*rq
, struct task_struct
*p
)
7889 update_rq_clock(rq
);
7895 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
7898 static void attach_tasks(struct lb_env
*env
)
7900 struct list_head
*tasks
= &env
->tasks
;
7901 struct task_struct
*p
;
7904 rq_lock(env
->dst_rq
, &rf
);
7905 update_rq_clock(env
->dst_rq
);
7907 while (!list_empty(tasks
)) {
7908 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
7909 list_del_init(&p
->se
.group_node
);
7911 attach_task(env
->dst_rq
, p
);
7914 rq_unlock(env
->dst_rq
, &rf
);
7917 #ifdef CONFIG_NO_HZ_COMMON
7918 static inline bool cfs_rq_has_blocked(struct cfs_rq
*cfs_rq
)
7920 if (cfs_rq
->avg
.load_avg
)
7923 if (cfs_rq
->avg
.util_avg
)
7929 static inline bool others_have_blocked(struct rq
*rq
)
7931 if (READ_ONCE(rq
->avg_rt
.util_avg
))
7934 if (READ_ONCE(rq
->avg_dl
.util_avg
))
7937 if (thermal_load_avg(rq
))
7940 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
7941 if (READ_ONCE(rq
->avg_irq
.util_avg
))
7948 static inline void update_blocked_load_tick(struct rq
*rq
)
7950 WRITE_ONCE(rq
->last_blocked_load_update_tick
, jiffies
);
7953 static inline void update_blocked_load_status(struct rq
*rq
, bool has_blocked
)
7956 rq
->has_blocked_load
= 0;
7959 static inline bool cfs_rq_has_blocked(struct cfs_rq
*cfs_rq
) { return false; }
7960 static inline bool others_have_blocked(struct rq
*rq
) { return false; }
7961 static inline void update_blocked_load_tick(struct rq
*rq
) {}
7962 static inline void update_blocked_load_status(struct rq
*rq
, bool has_blocked
) {}
7965 static bool __update_blocked_others(struct rq
*rq
, bool *done
)
7967 const struct sched_class
*curr_class
;
7968 u64 now
= rq_clock_pelt(rq
);
7969 unsigned long thermal_pressure
;
7973 * update_load_avg() can call cpufreq_update_util(). Make sure that RT,
7974 * DL and IRQ signals have been updated before updating CFS.
7976 curr_class
= rq
->curr
->sched_class
;
7978 thermal_pressure
= arch_scale_thermal_pressure(cpu_of(rq
));
7980 decayed
= update_rt_rq_load_avg(now
, rq
, curr_class
== &rt_sched_class
) |
7981 update_dl_rq_load_avg(now
, rq
, curr_class
== &dl_sched_class
) |
7982 update_thermal_load_avg(rq_clock_thermal(rq
), rq
, thermal_pressure
) |
7983 update_irq_load_avg(rq
, 0);
7985 if (others_have_blocked(rq
))
7991 #ifdef CONFIG_FAIR_GROUP_SCHED
7993 static inline bool cfs_rq_is_decayed(struct cfs_rq
*cfs_rq
)
7995 if (cfs_rq
->load
.weight
)
7998 if (cfs_rq
->avg
.load_sum
)
8001 if (cfs_rq
->avg
.util_sum
)
8004 if (cfs_rq
->avg
.runnable_sum
)
8010 static bool __update_blocked_fair(struct rq
*rq
, bool *done
)
8012 struct cfs_rq
*cfs_rq
, *pos
;
8013 bool decayed
= false;
8014 int cpu
= cpu_of(rq
);
8017 * Iterates the task_group tree in a bottom up fashion, see
8018 * list_add_leaf_cfs_rq() for details.
8020 for_each_leaf_cfs_rq_safe(rq
, cfs_rq
, pos
) {
8021 struct sched_entity
*se
;
8023 if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq
), cfs_rq
)) {
8024 update_tg_load_avg(cfs_rq
);
8026 if (cfs_rq
== &rq
->cfs
)
8030 /* Propagate pending load changes to the parent, if any: */
8031 se
= cfs_rq
->tg
->se
[cpu
];
8032 if (se
&& !skip_blocked_update(se
))
8033 update_load_avg(cfs_rq_of(se
), se
, 0);
8036 * There can be a lot of idle CPU cgroups. Don't let fully
8037 * decayed cfs_rqs linger on the list.
8039 if (cfs_rq_is_decayed(cfs_rq
))
8040 list_del_leaf_cfs_rq(cfs_rq
);
8042 /* Don't need periodic decay once load/util_avg are null */
8043 if (cfs_rq_has_blocked(cfs_rq
))
8051 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
8052 * This needs to be done in a top-down fashion because the load of a child
8053 * group is a fraction of its parents load.
8055 static void update_cfs_rq_h_load(struct cfs_rq
*cfs_rq
)
8057 struct rq
*rq
= rq_of(cfs_rq
);
8058 struct sched_entity
*se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
8059 unsigned long now
= jiffies
;
8062 if (cfs_rq
->last_h_load_update
== now
)
8065 WRITE_ONCE(cfs_rq
->h_load_next
, NULL
);
8066 for_each_sched_entity(se
) {
8067 cfs_rq
= cfs_rq_of(se
);
8068 WRITE_ONCE(cfs_rq
->h_load_next
, se
);
8069 if (cfs_rq
->last_h_load_update
== now
)
8074 cfs_rq
->h_load
= cfs_rq_load_avg(cfs_rq
);
8075 cfs_rq
->last_h_load_update
= now
;
8078 while ((se
= READ_ONCE(cfs_rq
->h_load_next
)) != NULL
) {
8079 load
= cfs_rq
->h_load
;
8080 load
= div64_ul(load
* se
->avg
.load_avg
,
8081 cfs_rq_load_avg(cfs_rq
) + 1);
8082 cfs_rq
= group_cfs_rq(se
);
8083 cfs_rq
->h_load
= load
;
8084 cfs_rq
->last_h_load_update
= now
;
8088 static unsigned long task_h_load(struct task_struct
*p
)
8090 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
8092 update_cfs_rq_h_load(cfs_rq
);
8093 return div64_ul(p
->se
.avg
.load_avg
* cfs_rq
->h_load
,
8094 cfs_rq_load_avg(cfs_rq
) + 1);
8097 static bool __update_blocked_fair(struct rq
*rq
, bool *done
)
8099 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
8102 decayed
= update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq
), cfs_rq
);
8103 if (cfs_rq_has_blocked(cfs_rq
))
8109 static unsigned long task_h_load(struct task_struct
*p
)
8111 return p
->se
.avg
.load_avg
;
8115 static void update_blocked_averages(int cpu
)
8117 bool decayed
= false, done
= true;
8118 struct rq
*rq
= cpu_rq(cpu
);
8121 rq_lock_irqsave(rq
, &rf
);
8122 update_blocked_load_tick(rq
);
8123 update_rq_clock(rq
);
8125 decayed
|= __update_blocked_others(rq
, &done
);
8126 decayed
|= __update_blocked_fair(rq
, &done
);
8128 update_blocked_load_status(rq
, !done
);
8130 cpufreq_update_util(rq
, 0);
8131 rq_unlock_irqrestore(rq
, &rf
);
8134 /********** Helpers for find_busiest_group ************************/
8137 * sg_lb_stats - stats of a sched_group required for load_balancing
8139 struct sg_lb_stats
{
8140 unsigned long avg_load
; /*Avg load across the CPUs of the group */
8141 unsigned long group_load
; /* Total load over the CPUs of the group */
8142 unsigned long group_capacity
;
8143 unsigned long group_util
; /* Total utilization over the CPUs of the group */
8144 unsigned long group_runnable
; /* Total runnable time over the CPUs of the group */
8145 unsigned int sum_nr_running
; /* Nr of tasks running in the group */
8146 unsigned int sum_h_nr_running
; /* Nr of CFS tasks running in the group */
8147 unsigned int idle_cpus
;
8148 unsigned int group_weight
;
8149 enum group_type group_type
;
8150 unsigned int group_asym_packing
; /* Tasks should be moved to preferred CPU */
8151 unsigned long group_misfit_task_load
; /* A CPU has a task too big for its capacity */
8152 #ifdef CONFIG_NUMA_BALANCING
8153 unsigned int nr_numa_running
;
8154 unsigned int nr_preferred_running
;
8159 * sd_lb_stats - Structure to store the statistics of a sched_domain
8160 * during load balancing.
8162 struct sd_lb_stats
{
8163 struct sched_group
*busiest
; /* Busiest group in this sd */
8164 struct sched_group
*local
; /* Local group in this sd */
8165 unsigned long total_load
; /* Total load of all groups in sd */
8166 unsigned long total_capacity
; /* Total capacity of all groups in sd */
8167 unsigned long avg_load
; /* Average load across all groups in sd */
8168 unsigned int prefer_sibling
; /* tasks should go to sibling first */
8170 struct sg_lb_stats busiest_stat
;/* Statistics of the busiest group */
8171 struct sg_lb_stats local_stat
; /* Statistics of the local group */
8174 static inline void init_sd_lb_stats(struct sd_lb_stats
*sds
)
8177 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
8178 * local_stat because update_sg_lb_stats() does a full clear/assignment.
8179 * We must however set busiest_stat::group_type and
8180 * busiest_stat::idle_cpus to the worst busiest group because
8181 * update_sd_pick_busiest() reads these before assignment.
8183 *sds
= (struct sd_lb_stats
){
8187 .total_capacity
= 0UL,
8189 .idle_cpus
= UINT_MAX
,
8190 .group_type
= group_has_spare
,
8195 static unsigned long scale_rt_capacity(int cpu
)
8197 struct rq
*rq
= cpu_rq(cpu
);
8198 unsigned long max
= arch_scale_cpu_capacity(cpu
);
8199 unsigned long used
, free
;
8202 irq
= cpu_util_irq(rq
);
8204 if (unlikely(irq
>= max
))
8208 * avg_rt.util_avg and avg_dl.util_avg track binary signals
8209 * (running and not running) with weights 0 and 1024 respectively.
8210 * avg_thermal.load_avg tracks thermal pressure and the weighted
8211 * average uses the actual delta max capacity(load).
8213 used
= READ_ONCE(rq
->avg_rt
.util_avg
);
8214 used
+= READ_ONCE(rq
->avg_dl
.util_avg
);
8215 used
+= thermal_load_avg(rq
);
8217 if (unlikely(used
>= max
))
8222 return scale_irq_capacity(free
, irq
, max
);
8225 static void update_cpu_capacity(struct sched_domain
*sd
, int cpu
)
8227 unsigned long capacity
= scale_rt_capacity(cpu
);
8228 struct sched_group
*sdg
= sd
->groups
;
8230 cpu_rq(cpu
)->cpu_capacity_orig
= arch_scale_cpu_capacity(cpu
);
8235 cpu_rq(cpu
)->cpu_capacity
= capacity
;
8236 trace_sched_cpu_capacity_tp(cpu_rq(cpu
));
8238 sdg
->sgc
->capacity
= capacity
;
8239 sdg
->sgc
->min_capacity
= capacity
;
8240 sdg
->sgc
->max_capacity
= capacity
;
8243 void update_group_capacity(struct sched_domain
*sd
, int cpu
)
8245 struct sched_domain
*child
= sd
->child
;
8246 struct sched_group
*group
, *sdg
= sd
->groups
;
8247 unsigned long capacity
, min_capacity
, max_capacity
;
8248 unsigned long interval
;
8250 interval
= msecs_to_jiffies(sd
->balance_interval
);
8251 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
8252 sdg
->sgc
->next_update
= jiffies
+ interval
;
8255 update_cpu_capacity(sd
, cpu
);
8260 min_capacity
= ULONG_MAX
;
8263 if (child
->flags
& SD_OVERLAP
) {
8265 * SD_OVERLAP domains cannot assume that child groups
8266 * span the current group.
8269 for_each_cpu(cpu
, sched_group_span(sdg
)) {
8270 unsigned long cpu_cap
= capacity_of(cpu
);
8272 capacity
+= cpu_cap
;
8273 min_capacity
= min(cpu_cap
, min_capacity
);
8274 max_capacity
= max(cpu_cap
, max_capacity
);
8278 * !SD_OVERLAP domains can assume that child groups
8279 * span the current group.
8282 group
= child
->groups
;
8284 struct sched_group_capacity
*sgc
= group
->sgc
;
8286 capacity
+= sgc
->capacity
;
8287 min_capacity
= min(sgc
->min_capacity
, min_capacity
);
8288 max_capacity
= max(sgc
->max_capacity
, max_capacity
);
8289 group
= group
->next
;
8290 } while (group
!= child
->groups
);
8293 sdg
->sgc
->capacity
= capacity
;
8294 sdg
->sgc
->min_capacity
= min_capacity
;
8295 sdg
->sgc
->max_capacity
= max_capacity
;
8299 * Check whether the capacity of the rq has been noticeably reduced by side
8300 * activity. The imbalance_pct is used for the threshold.
8301 * Return true is the capacity is reduced
8304 check_cpu_capacity(struct rq
*rq
, struct sched_domain
*sd
)
8306 return ((rq
->cpu_capacity
* sd
->imbalance_pct
) <
8307 (rq
->cpu_capacity_orig
* 100));
8311 * Check whether a rq has a misfit task and if it looks like we can actually
8312 * help that task: we can migrate the task to a CPU of higher capacity, or
8313 * the task's current CPU is heavily pressured.
8315 static inline int check_misfit_status(struct rq
*rq
, struct sched_domain
*sd
)
8317 return rq
->misfit_task_load
&&
8318 (rq
->cpu_capacity_orig
< rq
->rd
->max_cpu_capacity
||
8319 check_cpu_capacity(rq
, sd
));
8323 * Group imbalance indicates (and tries to solve) the problem where balancing
8324 * groups is inadequate due to ->cpus_ptr constraints.
8326 * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
8327 * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
8330 * { 0 1 2 3 } { 4 5 6 7 }
8333 * If we were to balance group-wise we'd place two tasks in the first group and
8334 * two tasks in the second group. Clearly this is undesired as it will overload
8335 * cpu 3 and leave one of the CPUs in the second group unused.
8337 * The current solution to this issue is detecting the skew in the first group
8338 * by noticing the lower domain failed to reach balance and had difficulty
8339 * moving tasks due to affinity constraints.
8341 * When this is so detected; this group becomes a candidate for busiest; see
8342 * update_sd_pick_busiest(). And calculate_imbalance() and
8343 * find_busiest_group() avoid some of the usual balance conditions to allow it
8344 * to create an effective group imbalance.
8346 * This is a somewhat tricky proposition since the next run might not find the
8347 * group imbalance and decide the groups need to be balanced again. A most
8348 * subtle and fragile situation.
8351 static inline int sg_imbalanced(struct sched_group
*group
)
8353 return group
->sgc
->imbalance
;
8357 * group_has_capacity returns true if the group has spare capacity that could
8358 * be used by some tasks.
8359 * We consider that a group has spare capacity if the * number of task is
8360 * smaller than the number of CPUs or if the utilization is lower than the
8361 * available capacity for CFS tasks.
8362 * For the latter, we use a threshold to stabilize the state, to take into
8363 * account the variance of the tasks' load and to return true if the available
8364 * capacity in meaningful for the load balancer.
8365 * As an example, an available capacity of 1% can appear but it doesn't make
8366 * any benefit for the load balance.
8369 group_has_capacity(unsigned int imbalance_pct
, struct sg_lb_stats
*sgs
)
8371 if (sgs
->sum_nr_running
< sgs
->group_weight
)
8374 if ((sgs
->group_capacity
* imbalance_pct
) <
8375 (sgs
->group_runnable
* 100))
8378 if ((sgs
->group_capacity
* 100) >
8379 (sgs
->group_util
* imbalance_pct
))
8386 * group_is_overloaded returns true if the group has more tasks than it can
8388 * group_is_overloaded is not equals to !group_has_capacity because a group
8389 * with the exact right number of tasks, has no more spare capacity but is not
8390 * overloaded so both group_has_capacity and group_is_overloaded return
8394 group_is_overloaded(unsigned int imbalance_pct
, struct sg_lb_stats
*sgs
)
8396 if (sgs
->sum_nr_running
<= sgs
->group_weight
)
8399 if ((sgs
->group_capacity
* 100) <
8400 (sgs
->group_util
* imbalance_pct
))
8403 if ((sgs
->group_capacity
* imbalance_pct
) <
8404 (sgs
->group_runnable
* 100))
8411 group_type
group_classify(unsigned int imbalance_pct
,
8412 struct sched_group
*group
,
8413 struct sg_lb_stats
*sgs
)
8415 if (group_is_overloaded(imbalance_pct
, sgs
))
8416 return group_overloaded
;
8418 if (sg_imbalanced(group
))
8419 return group_imbalanced
;
8421 if (sgs
->group_asym_packing
)
8422 return group_asym_packing
;
8424 if (sgs
->group_misfit_task_load
)
8425 return group_misfit_task
;
8427 if (!group_has_capacity(imbalance_pct
, sgs
))
8428 return group_fully_busy
;
8430 return group_has_spare
;
8434 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
8435 * @env: The load balancing environment.
8436 * @group: sched_group whose statistics are to be updated.
8437 * @sgs: variable to hold the statistics for this group.
8438 * @sg_status: Holds flag indicating the status of the sched_group
8440 static inline void update_sg_lb_stats(struct lb_env
*env
,
8441 struct sched_group
*group
,
8442 struct sg_lb_stats
*sgs
,
8445 int i
, nr_running
, local_group
;
8447 memset(sgs
, 0, sizeof(*sgs
));
8449 local_group
= cpumask_test_cpu(env
->dst_cpu
, sched_group_span(group
));
8451 for_each_cpu_and(i
, sched_group_span(group
), env
->cpus
) {
8452 struct rq
*rq
= cpu_rq(i
);
8454 sgs
->group_load
+= cpu_load(rq
);
8455 sgs
->group_util
+= cpu_util(i
);
8456 sgs
->group_runnable
+= cpu_runnable(rq
);
8457 sgs
->sum_h_nr_running
+= rq
->cfs
.h_nr_running
;
8459 nr_running
= rq
->nr_running
;
8460 sgs
->sum_nr_running
+= nr_running
;
8463 *sg_status
|= SG_OVERLOAD
;
8465 if (cpu_overutilized(i
))
8466 *sg_status
|= SG_OVERUTILIZED
;
8468 #ifdef CONFIG_NUMA_BALANCING
8469 sgs
->nr_numa_running
+= rq
->nr_numa_running
;
8470 sgs
->nr_preferred_running
+= rq
->nr_preferred_running
;
8473 * No need to call idle_cpu() if nr_running is not 0
8475 if (!nr_running
&& idle_cpu(i
)) {
8477 /* Idle cpu can't have misfit task */
8484 /* Check for a misfit task on the cpu */
8485 if (env
->sd
->flags
& SD_ASYM_CPUCAPACITY
&&
8486 sgs
->group_misfit_task_load
< rq
->misfit_task_load
) {
8487 sgs
->group_misfit_task_load
= rq
->misfit_task_load
;
8488 *sg_status
|= SG_OVERLOAD
;
8492 /* Check if dst CPU is idle and preferred to this group */
8493 if (env
->sd
->flags
& SD_ASYM_PACKING
&&
8494 env
->idle
!= CPU_NOT_IDLE
&&
8495 sgs
->sum_h_nr_running
&&
8496 sched_asym_prefer(env
->dst_cpu
, group
->asym_prefer_cpu
)) {
8497 sgs
->group_asym_packing
= 1;
8500 sgs
->group_capacity
= group
->sgc
->capacity
;
8502 sgs
->group_weight
= group
->group_weight
;
8504 sgs
->group_type
= group_classify(env
->sd
->imbalance_pct
, group
, sgs
);
8506 /* Computing avg_load makes sense only when group is overloaded */
8507 if (sgs
->group_type
== group_overloaded
)
8508 sgs
->avg_load
= (sgs
->group_load
* SCHED_CAPACITY_SCALE
) /
8509 sgs
->group_capacity
;
8513 * update_sd_pick_busiest - return 1 on busiest group
8514 * @env: The load balancing environment.
8515 * @sds: sched_domain statistics
8516 * @sg: sched_group candidate to be checked for being the busiest
8517 * @sgs: sched_group statistics
8519 * Determine if @sg is a busier group than the previously selected
8522 * Return: %true if @sg is a busier group than the previously selected
8523 * busiest group. %false otherwise.
8525 static bool update_sd_pick_busiest(struct lb_env
*env
,
8526 struct sd_lb_stats
*sds
,
8527 struct sched_group
*sg
,
8528 struct sg_lb_stats
*sgs
)
8530 struct sg_lb_stats
*busiest
= &sds
->busiest_stat
;
8532 /* Make sure that there is at least one task to pull */
8533 if (!sgs
->sum_h_nr_running
)
8537 * Don't try to pull misfit tasks we can't help.
8538 * We can use max_capacity here as reduction in capacity on some
8539 * CPUs in the group should either be possible to resolve
8540 * internally or be covered by avg_load imbalance (eventually).
8542 if (sgs
->group_type
== group_misfit_task
&&
8543 (!capacity_greater(capacity_of(env
->dst_cpu
), sg
->sgc
->max_capacity
) ||
8544 sds
->local_stat
.group_type
!= group_has_spare
))
8547 if (sgs
->group_type
> busiest
->group_type
)
8550 if (sgs
->group_type
< busiest
->group_type
)
8554 * The candidate and the current busiest group are the same type of
8555 * group. Let check which one is the busiest according to the type.
8558 switch (sgs
->group_type
) {
8559 case group_overloaded
:
8560 /* Select the overloaded group with highest avg_load. */
8561 if (sgs
->avg_load
<= busiest
->avg_load
)
8565 case group_imbalanced
:
8567 * Select the 1st imbalanced group as we don't have any way to
8568 * choose one more than another.
8572 case group_asym_packing
:
8573 /* Prefer to move from lowest priority CPU's work */
8574 if (sched_asym_prefer(sg
->asym_prefer_cpu
, sds
->busiest
->asym_prefer_cpu
))
8578 case group_misfit_task
:
8580 * If we have more than one misfit sg go with the biggest
8583 if (sgs
->group_misfit_task_load
< busiest
->group_misfit_task_load
)
8587 case group_fully_busy
:
8589 * Select the fully busy group with highest avg_load. In
8590 * theory, there is no need to pull task from such kind of
8591 * group because tasks have all compute capacity that they need
8592 * but we can still improve the overall throughput by reducing
8593 * contention when accessing shared HW resources.
8595 * XXX for now avg_load is not computed and always 0 so we
8596 * select the 1st one.
8598 if (sgs
->avg_load
<= busiest
->avg_load
)
8602 case group_has_spare
:
8604 * Select not overloaded group with lowest number of idle cpus
8605 * and highest number of running tasks. We could also compare
8606 * the spare capacity which is more stable but it can end up
8607 * that the group has less spare capacity but finally more idle
8608 * CPUs which means less opportunity to pull tasks.
8610 if (sgs
->idle_cpus
> busiest
->idle_cpus
)
8612 else if ((sgs
->idle_cpus
== busiest
->idle_cpus
) &&
8613 (sgs
->sum_nr_running
<= busiest
->sum_nr_running
))
8620 * Candidate sg has no more than one task per CPU and has higher
8621 * per-CPU capacity. Migrating tasks to less capable CPUs may harm
8622 * throughput. Maximize throughput, power/energy consequences are not
8625 if ((env
->sd
->flags
& SD_ASYM_CPUCAPACITY
) &&
8626 (sgs
->group_type
<= group_fully_busy
) &&
8627 (capacity_greater(sg
->sgc
->min_capacity
, capacity_of(env
->dst_cpu
))))
8633 #ifdef CONFIG_NUMA_BALANCING
8634 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
8636 if (sgs
->sum_h_nr_running
> sgs
->nr_numa_running
)
8638 if (sgs
->sum_h_nr_running
> sgs
->nr_preferred_running
)
8643 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
8645 if (rq
->nr_running
> rq
->nr_numa_running
)
8647 if (rq
->nr_running
> rq
->nr_preferred_running
)
8652 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
8657 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
8661 #endif /* CONFIG_NUMA_BALANCING */
8667 * task_running_on_cpu - return 1 if @p is running on @cpu.
8670 static unsigned int task_running_on_cpu(int cpu
, struct task_struct
*p
)
8672 /* Task has no contribution or is new */
8673 if (cpu
!= task_cpu(p
) || !READ_ONCE(p
->se
.avg
.last_update_time
))
8676 if (task_on_rq_queued(p
))
8683 * idle_cpu_without - would a given CPU be idle without p ?
8684 * @cpu: the processor on which idleness is tested.
8685 * @p: task which should be ignored.
8687 * Return: 1 if the CPU would be idle. 0 otherwise.
8689 static int idle_cpu_without(int cpu
, struct task_struct
*p
)
8691 struct rq
*rq
= cpu_rq(cpu
);
8693 if (rq
->curr
!= rq
->idle
&& rq
->curr
!= p
)
8697 * rq->nr_running can't be used but an updated version without the
8698 * impact of p on cpu must be used instead. The updated nr_running
8699 * be computed and tested before calling idle_cpu_without().
8703 if (rq
->ttwu_pending
)
8711 * update_sg_wakeup_stats - Update sched_group's statistics for wakeup.
8712 * @sd: The sched_domain level to look for idlest group.
8713 * @group: sched_group whose statistics are to be updated.
8714 * @sgs: variable to hold the statistics for this group.
8715 * @p: The task for which we look for the idlest group/CPU.
8717 static inline void update_sg_wakeup_stats(struct sched_domain
*sd
,
8718 struct sched_group
*group
,
8719 struct sg_lb_stats
*sgs
,
8720 struct task_struct
*p
)
8724 memset(sgs
, 0, sizeof(*sgs
));
8726 for_each_cpu(i
, sched_group_span(group
)) {
8727 struct rq
*rq
= cpu_rq(i
);
8730 sgs
->group_load
+= cpu_load_without(rq
, p
);
8731 sgs
->group_util
+= cpu_util_without(i
, p
);
8732 sgs
->group_runnable
+= cpu_runnable_without(rq
, p
);
8733 local
= task_running_on_cpu(i
, p
);
8734 sgs
->sum_h_nr_running
+= rq
->cfs
.h_nr_running
- local
;
8736 nr_running
= rq
->nr_running
- local
;
8737 sgs
->sum_nr_running
+= nr_running
;
8740 * No need to call idle_cpu_without() if nr_running is not 0
8742 if (!nr_running
&& idle_cpu_without(i
, p
))
8747 /* Check if task fits in the group */
8748 if (sd
->flags
& SD_ASYM_CPUCAPACITY
&&
8749 !task_fits_capacity(p
, group
->sgc
->max_capacity
)) {
8750 sgs
->group_misfit_task_load
= 1;
8753 sgs
->group_capacity
= group
->sgc
->capacity
;
8755 sgs
->group_weight
= group
->group_weight
;
8757 sgs
->group_type
= group_classify(sd
->imbalance_pct
, group
, sgs
);
8760 * Computing avg_load makes sense only when group is fully busy or
8763 if (sgs
->group_type
== group_fully_busy
||
8764 sgs
->group_type
== group_overloaded
)
8765 sgs
->avg_load
= (sgs
->group_load
* SCHED_CAPACITY_SCALE
) /
8766 sgs
->group_capacity
;
8769 static bool update_pick_idlest(struct sched_group
*idlest
,
8770 struct sg_lb_stats
*idlest_sgs
,
8771 struct sched_group
*group
,
8772 struct sg_lb_stats
*sgs
)
8774 if (sgs
->group_type
< idlest_sgs
->group_type
)
8777 if (sgs
->group_type
> idlest_sgs
->group_type
)
8781 * The candidate and the current idlest group are the same type of
8782 * group. Let check which one is the idlest according to the type.
8785 switch (sgs
->group_type
) {
8786 case group_overloaded
:
8787 case group_fully_busy
:
8788 /* Select the group with lowest avg_load. */
8789 if (idlest_sgs
->avg_load
<= sgs
->avg_load
)
8793 case group_imbalanced
:
8794 case group_asym_packing
:
8795 /* Those types are not used in the slow wakeup path */
8798 case group_misfit_task
:
8799 /* Select group with the highest max capacity */
8800 if (idlest
->sgc
->max_capacity
>= group
->sgc
->max_capacity
)
8804 case group_has_spare
:
8805 /* Select group with most idle CPUs */
8806 if (idlest_sgs
->idle_cpus
> sgs
->idle_cpus
)
8809 /* Select group with lowest group_util */
8810 if (idlest_sgs
->idle_cpus
== sgs
->idle_cpus
&&
8811 idlest_sgs
->group_util
<= sgs
->group_util
)
8821 * Allow a NUMA imbalance if busy CPUs is less than 25% of the domain.
8822 * This is an approximation as the number of running tasks may not be
8823 * related to the number of busy CPUs due to sched_setaffinity.
8825 static inline bool allow_numa_imbalance(int dst_running
, int dst_weight
)
8827 return (dst_running
< (dst_weight
>> 2));
8831 * find_idlest_group() finds and returns the least busy CPU group within the
8834 * Assumes p is allowed on at least one CPU in sd.
8836 static struct sched_group
*
8837 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
, int this_cpu
)
8839 struct sched_group
*idlest
= NULL
, *local
= NULL
, *group
= sd
->groups
;
8840 struct sg_lb_stats local_sgs
, tmp_sgs
;
8841 struct sg_lb_stats
*sgs
;
8842 unsigned long imbalance
;
8843 struct sg_lb_stats idlest_sgs
= {
8844 .avg_load
= UINT_MAX
,
8845 .group_type
= group_overloaded
,
8851 /* Skip over this group if it has no CPUs allowed */
8852 if (!cpumask_intersects(sched_group_span(group
),
8856 local_group
= cpumask_test_cpu(this_cpu
,
8857 sched_group_span(group
));
8866 update_sg_wakeup_stats(sd
, group
, sgs
, p
);
8868 if (!local_group
&& update_pick_idlest(idlest
, &idlest_sgs
, group
, sgs
)) {
8873 } while (group
= group
->next
, group
!= sd
->groups
);
8876 /* There is no idlest group to push tasks to */
8880 /* The local group has been skipped because of CPU affinity */
8885 * If the local group is idler than the selected idlest group
8886 * don't try and push the task.
8888 if (local_sgs
.group_type
< idlest_sgs
.group_type
)
8892 * If the local group is busier than the selected idlest group
8893 * try and push the task.
8895 if (local_sgs
.group_type
> idlest_sgs
.group_type
)
8898 switch (local_sgs
.group_type
) {
8899 case group_overloaded
:
8900 case group_fully_busy
:
8902 /* Calculate allowed imbalance based on load */
8903 imbalance
= scale_load_down(NICE_0_LOAD
) *
8904 (sd
->imbalance_pct
-100) / 100;
8907 * When comparing groups across NUMA domains, it's possible for
8908 * the local domain to be very lightly loaded relative to the
8909 * remote domains but "imbalance" skews the comparison making
8910 * remote CPUs look much more favourable. When considering
8911 * cross-domain, add imbalance to the load on the remote node
8912 * and consider staying local.
8915 if ((sd
->flags
& SD_NUMA
) &&
8916 ((idlest_sgs
.avg_load
+ imbalance
) >= local_sgs
.avg_load
))
8920 * If the local group is less loaded than the selected
8921 * idlest group don't try and push any tasks.
8923 if (idlest_sgs
.avg_load
>= (local_sgs
.avg_load
+ imbalance
))
8926 if (100 * local_sgs
.avg_load
<= sd
->imbalance_pct
* idlest_sgs
.avg_load
)
8930 case group_imbalanced
:
8931 case group_asym_packing
:
8932 /* Those type are not used in the slow wakeup path */
8935 case group_misfit_task
:
8936 /* Select group with the highest max capacity */
8937 if (local
->sgc
->max_capacity
>= idlest
->sgc
->max_capacity
)
8941 case group_has_spare
:
8942 if (sd
->flags
& SD_NUMA
) {
8943 #ifdef CONFIG_NUMA_BALANCING
8946 * If there is spare capacity at NUMA, try to select
8947 * the preferred node
8949 if (cpu_to_node(this_cpu
) == p
->numa_preferred_nid
)
8952 idlest_cpu
= cpumask_first(sched_group_span(idlest
));
8953 if (cpu_to_node(idlest_cpu
) == p
->numa_preferred_nid
)
8957 * Otherwise, keep the task on this node to stay close
8958 * its wakeup source and improve locality. If there is
8959 * a real need of migration, periodic load balance will
8962 if (allow_numa_imbalance(local_sgs
.sum_nr_running
, sd
->span_weight
))
8967 * Select group with highest number of idle CPUs. We could also
8968 * compare the utilization which is more stable but it can end
8969 * up that the group has less spare capacity but finally more
8970 * idle CPUs which means more opportunity to run task.
8972 if (local_sgs
.idle_cpus
>= idlest_sgs
.idle_cpus
)
8981 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
8982 * @env: The load balancing environment.
8983 * @sds: variable to hold the statistics for this sched_domain.
8986 static inline void update_sd_lb_stats(struct lb_env
*env
, struct sd_lb_stats
*sds
)
8988 struct sched_domain
*child
= env
->sd
->child
;
8989 struct sched_group
*sg
= env
->sd
->groups
;
8990 struct sg_lb_stats
*local
= &sds
->local_stat
;
8991 struct sg_lb_stats tmp_sgs
;
8995 struct sg_lb_stats
*sgs
= &tmp_sgs
;
8998 local_group
= cpumask_test_cpu(env
->dst_cpu
, sched_group_span(sg
));
9003 if (env
->idle
!= CPU_NEWLY_IDLE
||
9004 time_after_eq(jiffies
, sg
->sgc
->next_update
))
9005 update_group_capacity(env
->sd
, env
->dst_cpu
);
9008 update_sg_lb_stats(env
, sg
, sgs
, &sg_status
);
9014 if (update_sd_pick_busiest(env
, sds
, sg
, sgs
)) {
9016 sds
->busiest_stat
= *sgs
;
9020 /* Now, start updating sd_lb_stats */
9021 sds
->total_load
+= sgs
->group_load
;
9022 sds
->total_capacity
+= sgs
->group_capacity
;
9025 } while (sg
!= env
->sd
->groups
);
9027 /* Tag domain that child domain prefers tasks go to siblings first */
9028 sds
->prefer_sibling
= child
&& child
->flags
& SD_PREFER_SIBLING
;
9031 if (env
->sd
->flags
& SD_NUMA
)
9032 env
->fbq_type
= fbq_classify_group(&sds
->busiest_stat
);
9034 if (!env
->sd
->parent
) {
9035 struct root_domain
*rd
= env
->dst_rq
->rd
;
9037 /* update overload indicator if we are at root domain */
9038 WRITE_ONCE(rd
->overload
, sg_status
& SG_OVERLOAD
);
9040 /* Update over-utilization (tipping point, U >= 0) indicator */
9041 WRITE_ONCE(rd
->overutilized
, sg_status
& SG_OVERUTILIZED
);
9042 trace_sched_overutilized_tp(rd
, sg_status
& SG_OVERUTILIZED
);
9043 } else if (sg_status
& SG_OVERUTILIZED
) {
9044 struct root_domain
*rd
= env
->dst_rq
->rd
;
9046 WRITE_ONCE(rd
->overutilized
, SG_OVERUTILIZED
);
9047 trace_sched_overutilized_tp(rd
, SG_OVERUTILIZED
);
9051 #define NUMA_IMBALANCE_MIN 2
9053 static inline long adjust_numa_imbalance(int imbalance
,
9054 int dst_running
, int dst_weight
)
9056 if (!allow_numa_imbalance(dst_running
, dst_weight
))
9060 * Allow a small imbalance based on a simple pair of communicating
9061 * tasks that remain local when the destination is lightly loaded.
9063 if (imbalance
<= NUMA_IMBALANCE_MIN
)
9070 * calculate_imbalance - Calculate the amount of imbalance present within the
9071 * groups of a given sched_domain during load balance.
9072 * @env: load balance environment
9073 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
9075 static inline void calculate_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
9077 struct sg_lb_stats
*local
, *busiest
;
9079 local
= &sds
->local_stat
;
9080 busiest
= &sds
->busiest_stat
;
9082 if (busiest
->group_type
== group_misfit_task
) {
9083 /* Set imbalance to allow misfit tasks to be balanced. */
9084 env
->migration_type
= migrate_misfit
;
9089 if (busiest
->group_type
== group_asym_packing
) {
9091 * In case of asym capacity, we will try to migrate all load to
9092 * the preferred CPU.
9094 env
->migration_type
= migrate_task
;
9095 env
->imbalance
= busiest
->sum_h_nr_running
;
9099 if (busiest
->group_type
== group_imbalanced
) {
9101 * In the group_imb case we cannot rely on group-wide averages
9102 * to ensure CPU-load equilibrium, try to move any task to fix
9103 * the imbalance. The next load balance will take care of
9104 * balancing back the system.
9106 env
->migration_type
= migrate_task
;
9112 * Try to use spare capacity of local group without overloading it or
9115 if (local
->group_type
== group_has_spare
) {
9116 if ((busiest
->group_type
> group_fully_busy
) &&
9117 !(env
->sd
->flags
& SD_SHARE_PKG_RESOURCES
)) {
9119 * If busiest is overloaded, try to fill spare
9120 * capacity. This might end up creating spare capacity
9121 * in busiest or busiest still being overloaded but
9122 * there is no simple way to directly compute the
9123 * amount of load to migrate in order to balance the
9126 env
->migration_type
= migrate_util
;
9127 env
->imbalance
= max(local
->group_capacity
, local
->group_util
) -
9131 * In some cases, the group's utilization is max or even
9132 * higher than capacity because of migrations but the
9133 * local CPU is (newly) idle. There is at least one
9134 * waiting task in this overloaded busiest group. Let's
9137 if (env
->idle
!= CPU_NOT_IDLE
&& env
->imbalance
== 0) {
9138 env
->migration_type
= migrate_task
;
9145 if (busiest
->group_weight
== 1 || sds
->prefer_sibling
) {
9146 unsigned int nr_diff
= busiest
->sum_nr_running
;
9148 * When prefer sibling, evenly spread running tasks on
9151 env
->migration_type
= migrate_task
;
9152 lsub_positive(&nr_diff
, local
->sum_nr_running
);
9153 env
->imbalance
= nr_diff
>> 1;
9157 * If there is no overload, we just want to even the number of
9160 env
->migration_type
= migrate_task
;
9161 env
->imbalance
= max_t(long, 0, (local
->idle_cpus
-
9162 busiest
->idle_cpus
) >> 1);
9165 /* Consider allowing a small imbalance between NUMA groups */
9166 if (env
->sd
->flags
& SD_NUMA
) {
9167 env
->imbalance
= adjust_numa_imbalance(env
->imbalance
,
9168 busiest
->sum_nr_running
, busiest
->group_weight
);
9175 * Local is fully busy but has to take more load to relieve the
9178 if (local
->group_type
< group_overloaded
) {
9180 * Local will become overloaded so the avg_load metrics are
9184 local
->avg_load
= (local
->group_load
* SCHED_CAPACITY_SCALE
) /
9185 local
->group_capacity
;
9187 sds
->avg_load
= (sds
->total_load
* SCHED_CAPACITY_SCALE
) /
9188 sds
->total_capacity
;
9190 * If the local group is more loaded than the selected
9191 * busiest group don't try to pull any tasks.
9193 if (local
->avg_load
>= busiest
->avg_load
) {
9200 * Both group are or will become overloaded and we're trying to get all
9201 * the CPUs to the average_load, so we don't want to push ourselves
9202 * above the average load, nor do we wish to reduce the max loaded CPU
9203 * below the average load. At the same time, we also don't want to
9204 * reduce the group load below the group capacity. Thus we look for
9205 * the minimum possible imbalance.
9207 env
->migration_type
= migrate_load
;
9208 env
->imbalance
= min(
9209 (busiest
->avg_load
- sds
->avg_load
) * busiest
->group_capacity
,
9210 (sds
->avg_load
- local
->avg_load
) * local
->group_capacity
9211 ) / SCHED_CAPACITY_SCALE
;
9214 /******* find_busiest_group() helpers end here *********************/
9217 * Decision matrix according to the local and busiest group type:
9219 * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
9220 * has_spare nr_idle balanced N/A N/A balanced balanced
9221 * fully_busy nr_idle nr_idle N/A N/A balanced balanced
9222 * misfit_task force N/A N/A N/A force force
9223 * asym_packing force force N/A N/A force force
9224 * imbalanced force force N/A N/A force force
9225 * overloaded force force N/A N/A force avg_load
9227 * N/A : Not Applicable because already filtered while updating
9229 * balanced : The system is balanced for these 2 groups.
9230 * force : Calculate the imbalance as load migration is probably needed.
9231 * avg_load : Only if imbalance is significant enough.
9232 * nr_idle : dst_cpu is not busy and the number of idle CPUs is quite
9233 * different in groups.
9237 * find_busiest_group - Returns the busiest group within the sched_domain
9238 * if there is an imbalance.
9240 * Also calculates the amount of runnable load which should be moved
9241 * to restore balance.
9243 * @env: The load balancing environment.
9245 * Return: - The busiest group if imbalance exists.
9247 static struct sched_group
*find_busiest_group(struct lb_env
*env
)
9249 struct sg_lb_stats
*local
, *busiest
;
9250 struct sd_lb_stats sds
;
9252 init_sd_lb_stats(&sds
);
9255 * Compute the various statistics relevant for load balancing at
9258 update_sd_lb_stats(env
, &sds
);
9260 if (sched_energy_enabled()) {
9261 struct root_domain
*rd
= env
->dst_rq
->rd
;
9263 if (rcu_dereference(rd
->pd
) && !READ_ONCE(rd
->overutilized
))
9267 local
= &sds
.local_stat
;
9268 busiest
= &sds
.busiest_stat
;
9270 /* There is no busy sibling group to pull tasks from */
9274 /* Misfit tasks should be dealt with regardless of the avg load */
9275 if (busiest
->group_type
== group_misfit_task
)
9278 /* ASYM feature bypasses nice load balance check */
9279 if (busiest
->group_type
== group_asym_packing
)
9283 * If the busiest group is imbalanced the below checks don't
9284 * work because they assume all things are equal, which typically
9285 * isn't true due to cpus_ptr constraints and the like.
9287 if (busiest
->group_type
== group_imbalanced
)
9291 * If the local group is busier than the selected busiest group
9292 * don't try and pull any tasks.
9294 if (local
->group_type
> busiest
->group_type
)
9298 * When groups are overloaded, use the avg_load to ensure fairness
9301 if (local
->group_type
== group_overloaded
) {
9303 * If the local group is more loaded than the selected
9304 * busiest group don't try to pull any tasks.
9306 if (local
->avg_load
>= busiest
->avg_load
)
9309 /* XXX broken for overlapping NUMA groups */
9310 sds
.avg_load
= (sds
.total_load
* SCHED_CAPACITY_SCALE
) /
9314 * Don't pull any tasks if this group is already above the
9315 * domain average load.
9317 if (local
->avg_load
>= sds
.avg_load
)
9321 * If the busiest group is more loaded, use imbalance_pct to be
9324 if (100 * busiest
->avg_load
<=
9325 env
->sd
->imbalance_pct
* local
->avg_load
)
9329 /* Try to move all excess tasks to child's sibling domain */
9330 if (sds
.prefer_sibling
&& local
->group_type
== group_has_spare
&&
9331 busiest
->sum_nr_running
> local
->sum_nr_running
+ 1)
9334 if (busiest
->group_type
!= group_overloaded
) {
9335 if (env
->idle
== CPU_NOT_IDLE
)
9337 * If the busiest group is not overloaded (and as a
9338 * result the local one too) but this CPU is already
9339 * busy, let another idle CPU try to pull task.
9343 if (busiest
->group_weight
> 1 &&
9344 local
->idle_cpus
<= (busiest
->idle_cpus
+ 1))
9346 * If the busiest group is not overloaded
9347 * and there is no imbalance between this and busiest
9348 * group wrt idle CPUs, it is balanced. The imbalance
9349 * becomes significant if the diff is greater than 1
9350 * otherwise we might end up to just move the imbalance
9351 * on another group. Of course this applies only if
9352 * there is more than 1 CPU per group.
9356 if (busiest
->sum_h_nr_running
== 1)
9358 * busiest doesn't have any tasks waiting to run
9364 /* Looks like there is an imbalance. Compute it */
9365 calculate_imbalance(env
, &sds
);
9366 return env
->imbalance
? sds
.busiest
: NULL
;
9374 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
9376 static struct rq
*find_busiest_queue(struct lb_env
*env
,
9377 struct sched_group
*group
)
9379 struct rq
*busiest
= NULL
, *rq
;
9380 unsigned long busiest_util
= 0, busiest_load
= 0, busiest_capacity
= 1;
9381 unsigned int busiest_nr
= 0;
9384 for_each_cpu_and(i
, sched_group_span(group
), env
->cpus
) {
9385 unsigned long capacity
, load
, util
;
9386 unsigned int nr_running
;
9390 rt
= fbq_classify_rq(rq
);
9393 * We classify groups/runqueues into three groups:
9394 * - regular: there are !numa tasks
9395 * - remote: there are numa tasks that run on the 'wrong' node
9396 * - all: there is no distinction
9398 * In order to avoid migrating ideally placed numa tasks,
9399 * ignore those when there's better options.
9401 * If we ignore the actual busiest queue to migrate another
9402 * task, the next balance pass can still reduce the busiest
9403 * queue by moving tasks around inside the node.
9405 * If we cannot move enough load due to this classification
9406 * the next pass will adjust the group classification and
9407 * allow migration of more tasks.
9409 * Both cases only affect the total convergence complexity.
9411 if (rt
> env
->fbq_type
)
9414 nr_running
= rq
->cfs
.h_nr_running
;
9418 capacity
= capacity_of(i
);
9421 * For ASYM_CPUCAPACITY domains, don't pick a CPU that could
9422 * eventually lead to active_balancing high->low capacity.
9423 * Higher per-CPU capacity is considered better than balancing
9426 if (env
->sd
->flags
& SD_ASYM_CPUCAPACITY
&&
9427 !capacity_greater(capacity_of(env
->dst_cpu
), capacity
) &&
9431 switch (env
->migration_type
) {
9434 * When comparing with load imbalance, use cpu_load()
9435 * which is not scaled with the CPU capacity.
9437 load
= cpu_load(rq
);
9439 if (nr_running
== 1 && load
> env
->imbalance
&&
9440 !check_cpu_capacity(rq
, env
->sd
))
9444 * For the load comparisons with the other CPUs,
9445 * consider the cpu_load() scaled with the CPU
9446 * capacity, so that the load can be moved away
9447 * from the CPU that is potentially running at a
9450 * Thus we're looking for max(load_i / capacity_i),
9451 * crosswise multiplication to rid ourselves of the
9452 * division works out to:
9453 * load_i * capacity_j > load_j * capacity_i;
9454 * where j is our previous maximum.
9456 if (load
* busiest_capacity
> busiest_load
* capacity
) {
9457 busiest_load
= load
;
9458 busiest_capacity
= capacity
;
9464 util
= cpu_util(cpu_of(rq
));
9467 * Don't try to pull utilization from a CPU with one
9468 * running task. Whatever its utilization, we will fail
9471 if (nr_running
<= 1)
9474 if (busiest_util
< util
) {
9475 busiest_util
= util
;
9481 if (busiest_nr
< nr_running
) {
9482 busiest_nr
= nr_running
;
9487 case migrate_misfit
:
9489 * For ASYM_CPUCAPACITY domains with misfit tasks we
9490 * simply seek the "biggest" misfit task.
9492 if (rq
->misfit_task_load
> busiest_load
) {
9493 busiest_load
= rq
->misfit_task_load
;
9506 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
9507 * so long as it is large enough.
9509 #define MAX_PINNED_INTERVAL 512
9512 asym_active_balance(struct lb_env
*env
)
9515 * ASYM_PACKING needs to force migrate tasks from busy but
9516 * lower priority CPUs in order to pack all tasks in the
9517 * highest priority CPUs.
9519 return env
->idle
!= CPU_NOT_IDLE
&& (env
->sd
->flags
& SD_ASYM_PACKING
) &&
9520 sched_asym_prefer(env
->dst_cpu
, env
->src_cpu
);
9524 imbalanced_active_balance(struct lb_env
*env
)
9526 struct sched_domain
*sd
= env
->sd
;
9529 * The imbalanced case includes the case of pinned tasks preventing a fair
9530 * distribution of the load on the system but also the even distribution of the
9531 * threads on a system with spare capacity
9533 if ((env
->migration_type
== migrate_task
) &&
9534 (sd
->nr_balance_failed
> sd
->cache_nice_tries
+2))
9540 static int need_active_balance(struct lb_env
*env
)
9542 struct sched_domain
*sd
= env
->sd
;
9544 if (asym_active_balance(env
))
9547 if (imbalanced_active_balance(env
))
9551 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
9552 * It's worth migrating the task if the src_cpu's capacity is reduced
9553 * because of other sched_class or IRQs if more capacity stays
9554 * available on dst_cpu.
9556 if ((env
->idle
!= CPU_NOT_IDLE
) &&
9557 (env
->src_rq
->cfs
.h_nr_running
== 1)) {
9558 if ((check_cpu_capacity(env
->src_rq
, sd
)) &&
9559 (capacity_of(env
->src_cpu
)*sd
->imbalance_pct
< capacity_of(env
->dst_cpu
)*100))
9563 if (env
->migration_type
== migrate_misfit
)
9569 static int active_load_balance_cpu_stop(void *data
);
9571 static int should_we_balance(struct lb_env
*env
)
9573 struct sched_group
*sg
= env
->sd
->groups
;
9577 * Ensure the balancing environment is consistent; can happen
9578 * when the softirq triggers 'during' hotplug.
9580 if (!cpumask_test_cpu(env
->dst_cpu
, env
->cpus
))
9584 * In the newly idle case, we will allow all the CPUs
9585 * to do the newly idle load balance.
9587 if (env
->idle
== CPU_NEWLY_IDLE
)
9590 /* Try to find first idle CPU */
9591 for_each_cpu_and(cpu
, group_balance_mask(sg
), env
->cpus
) {
9595 /* Are we the first idle CPU? */
9596 return cpu
== env
->dst_cpu
;
9599 /* Are we the first CPU of this group ? */
9600 return group_balance_cpu(sg
) == env
->dst_cpu
;
9604 * Check this_cpu to ensure it is balanced within domain. Attempt to move
9605 * tasks if there is an imbalance.
9607 static int load_balance(int this_cpu
, struct rq
*this_rq
,
9608 struct sched_domain
*sd
, enum cpu_idle_type idle
,
9609 int *continue_balancing
)
9611 int ld_moved
, cur_ld_moved
, active_balance
= 0;
9612 struct sched_domain
*sd_parent
= sd
->parent
;
9613 struct sched_group
*group
;
9616 struct cpumask
*cpus
= this_cpu_cpumask_var_ptr(load_balance_mask
);
9618 struct lb_env env
= {
9620 .dst_cpu
= this_cpu
,
9622 .dst_grpmask
= sched_group_span(sd
->groups
),
9624 .loop_break
= sched_nr_migrate_break
,
9627 .tasks
= LIST_HEAD_INIT(env
.tasks
),
9630 cpumask_and(cpus
, sched_domain_span(sd
), cpu_active_mask
);
9632 schedstat_inc(sd
->lb_count
[idle
]);
9635 if (!should_we_balance(&env
)) {
9636 *continue_balancing
= 0;
9640 group
= find_busiest_group(&env
);
9642 schedstat_inc(sd
->lb_nobusyg
[idle
]);
9646 busiest
= find_busiest_queue(&env
, group
);
9648 schedstat_inc(sd
->lb_nobusyq
[idle
]);
9652 BUG_ON(busiest
== env
.dst_rq
);
9654 schedstat_add(sd
->lb_imbalance
[idle
], env
.imbalance
);
9656 env
.src_cpu
= busiest
->cpu
;
9657 env
.src_rq
= busiest
;
9660 /* Clear this flag as soon as we find a pullable task */
9661 env
.flags
|= LBF_ALL_PINNED
;
9662 if (busiest
->nr_running
> 1) {
9664 * Attempt to move tasks. If find_busiest_group has found
9665 * an imbalance but busiest->nr_running <= 1, the group is
9666 * still unbalanced. ld_moved simply stays zero, so it is
9667 * correctly treated as an imbalance.
9669 env
.loop_max
= min(sysctl_sched_nr_migrate
, busiest
->nr_running
);
9672 rq_lock_irqsave(busiest
, &rf
);
9673 update_rq_clock(busiest
);
9676 * cur_ld_moved - load moved in current iteration
9677 * ld_moved - cumulative load moved across iterations
9679 cur_ld_moved
= detach_tasks(&env
);
9682 * We've detached some tasks from busiest_rq. Every
9683 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
9684 * unlock busiest->lock, and we are able to be sure
9685 * that nobody can manipulate the tasks in parallel.
9686 * See task_rq_lock() family for the details.
9689 rq_unlock(busiest
, &rf
);
9693 ld_moved
+= cur_ld_moved
;
9696 local_irq_restore(rf
.flags
);
9698 if (env
.flags
& LBF_NEED_BREAK
) {
9699 env
.flags
&= ~LBF_NEED_BREAK
;
9704 * Revisit (affine) tasks on src_cpu that couldn't be moved to
9705 * us and move them to an alternate dst_cpu in our sched_group
9706 * where they can run. The upper limit on how many times we
9707 * iterate on same src_cpu is dependent on number of CPUs in our
9710 * This changes load balance semantics a bit on who can move
9711 * load to a given_cpu. In addition to the given_cpu itself
9712 * (or a ilb_cpu acting on its behalf where given_cpu is
9713 * nohz-idle), we now have balance_cpu in a position to move
9714 * load to given_cpu. In rare situations, this may cause
9715 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
9716 * _independently_ and at _same_ time to move some load to
9717 * given_cpu) causing excess load to be moved to given_cpu.
9718 * This however should not happen so much in practice and
9719 * moreover subsequent load balance cycles should correct the
9720 * excess load moved.
9722 if ((env
.flags
& LBF_DST_PINNED
) && env
.imbalance
> 0) {
9724 /* Prevent to re-select dst_cpu via env's CPUs */
9725 __cpumask_clear_cpu(env
.dst_cpu
, env
.cpus
);
9727 env
.dst_rq
= cpu_rq(env
.new_dst_cpu
);
9728 env
.dst_cpu
= env
.new_dst_cpu
;
9729 env
.flags
&= ~LBF_DST_PINNED
;
9731 env
.loop_break
= sched_nr_migrate_break
;
9734 * Go back to "more_balance" rather than "redo" since we
9735 * need to continue with same src_cpu.
9741 * We failed to reach balance because of affinity.
9744 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
9746 if ((env
.flags
& LBF_SOME_PINNED
) && env
.imbalance
> 0)
9747 *group_imbalance
= 1;
9750 /* All tasks on this runqueue were pinned by CPU affinity */
9751 if (unlikely(env
.flags
& LBF_ALL_PINNED
)) {
9752 __cpumask_clear_cpu(cpu_of(busiest
), cpus
);
9754 * Attempting to continue load balancing at the current
9755 * sched_domain level only makes sense if there are
9756 * active CPUs remaining as possible busiest CPUs to
9757 * pull load from which are not contained within the
9758 * destination group that is receiving any migrated
9761 if (!cpumask_subset(cpus
, env
.dst_grpmask
)) {
9763 env
.loop_break
= sched_nr_migrate_break
;
9766 goto out_all_pinned
;
9771 schedstat_inc(sd
->lb_failed
[idle
]);
9773 * Increment the failure counter only on periodic balance.
9774 * We do not want newidle balance, which can be very
9775 * frequent, pollute the failure counter causing
9776 * excessive cache_hot migrations and active balances.
9778 if (idle
!= CPU_NEWLY_IDLE
)
9779 sd
->nr_balance_failed
++;
9781 if (need_active_balance(&env
)) {
9782 unsigned long flags
;
9784 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
9787 * Don't kick the active_load_balance_cpu_stop,
9788 * if the curr task on busiest CPU can't be
9789 * moved to this_cpu:
9791 if (!cpumask_test_cpu(this_cpu
, busiest
->curr
->cpus_ptr
)) {
9792 raw_spin_unlock_irqrestore(&busiest
->lock
,
9794 goto out_one_pinned
;
9797 /* Record that we found at least one task that could run on this_cpu */
9798 env
.flags
&= ~LBF_ALL_PINNED
;
9801 * ->active_balance synchronizes accesses to
9802 * ->active_balance_work. Once set, it's cleared
9803 * only after active load balance is finished.
9805 if (!busiest
->active_balance
) {
9806 busiest
->active_balance
= 1;
9807 busiest
->push_cpu
= this_cpu
;
9810 raw_spin_unlock_irqrestore(&busiest
->lock
, flags
);
9812 if (active_balance
) {
9813 stop_one_cpu_nowait(cpu_of(busiest
),
9814 active_load_balance_cpu_stop
, busiest
,
9815 &busiest
->active_balance_work
);
9819 sd
->nr_balance_failed
= 0;
9822 if (likely(!active_balance
) || need_active_balance(&env
)) {
9823 /* We were unbalanced, so reset the balancing interval */
9824 sd
->balance_interval
= sd
->min_interval
;
9831 * We reach balance although we may have faced some affinity
9832 * constraints. Clear the imbalance flag only if other tasks got
9833 * a chance to move and fix the imbalance.
9835 if (sd_parent
&& !(env
.flags
& LBF_ALL_PINNED
)) {
9836 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
9838 if (*group_imbalance
)
9839 *group_imbalance
= 0;
9844 * We reach balance because all tasks are pinned at this level so
9845 * we can't migrate them. Let the imbalance flag set so parent level
9846 * can try to migrate them.
9848 schedstat_inc(sd
->lb_balanced
[idle
]);
9850 sd
->nr_balance_failed
= 0;
9856 * newidle_balance() disregards balance intervals, so we could
9857 * repeatedly reach this code, which would lead to balance_interval
9858 * skyrocketing in a short amount of time. Skip the balance_interval
9859 * increase logic to avoid that.
9861 if (env
.idle
== CPU_NEWLY_IDLE
)
9864 /* tune up the balancing interval */
9865 if ((env
.flags
& LBF_ALL_PINNED
&&
9866 sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
9867 sd
->balance_interval
< sd
->max_interval
)
9868 sd
->balance_interval
*= 2;
9873 static inline unsigned long
9874 get_sd_balance_interval(struct sched_domain
*sd
, int cpu_busy
)
9876 unsigned long interval
= sd
->balance_interval
;
9879 interval
*= sd
->busy_factor
;
9881 /* scale ms to jiffies */
9882 interval
= msecs_to_jiffies(interval
);
9885 * Reduce likelihood of busy balancing at higher domains racing with
9886 * balancing at lower domains by preventing their balancing periods
9887 * from being multiples of each other.
9892 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
9898 update_next_balance(struct sched_domain
*sd
, unsigned long *next_balance
)
9900 unsigned long interval
, next
;
9902 /* used by idle balance, so cpu_busy = 0 */
9903 interval
= get_sd_balance_interval(sd
, 0);
9904 next
= sd
->last_balance
+ interval
;
9906 if (time_after(*next_balance
, next
))
9907 *next_balance
= next
;
9911 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
9912 * running tasks off the busiest CPU onto idle CPUs. It requires at
9913 * least 1 task to be running on each physical CPU where possible, and
9914 * avoids physical / logical imbalances.
9916 static int active_load_balance_cpu_stop(void *data
)
9918 struct rq
*busiest_rq
= data
;
9919 int busiest_cpu
= cpu_of(busiest_rq
);
9920 int target_cpu
= busiest_rq
->push_cpu
;
9921 struct rq
*target_rq
= cpu_rq(target_cpu
);
9922 struct sched_domain
*sd
;
9923 struct task_struct
*p
= NULL
;
9926 rq_lock_irq(busiest_rq
, &rf
);
9928 * Between queueing the stop-work and running it is a hole in which
9929 * CPUs can become inactive. We should not move tasks from or to
9932 if (!cpu_active(busiest_cpu
) || !cpu_active(target_cpu
))
9935 /* Make sure the requested CPU hasn't gone down in the meantime: */
9936 if (unlikely(busiest_cpu
!= smp_processor_id() ||
9937 !busiest_rq
->active_balance
))
9940 /* Is there any task to move? */
9941 if (busiest_rq
->nr_running
<= 1)
9945 * This condition is "impossible", if it occurs
9946 * we need to fix it. Originally reported by
9947 * Bjorn Helgaas on a 128-CPU setup.
9949 BUG_ON(busiest_rq
== target_rq
);
9951 /* Search for an sd spanning us and the target CPU. */
9953 for_each_domain(target_cpu
, sd
) {
9954 if (cpumask_test_cpu(busiest_cpu
, sched_domain_span(sd
)))
9959 struct lb_env env
= {
9961 .dst_cpu
= target_cpu
,
9962 .dst_rq
= target_rq
,
9963 .src_cpu
= busiest_rq
->cpu
,
9964 .src_rq
= busiest_rq
,
9966 .flags
= LBF_ACTIVE_LB
,
9969 schedstat_inc(sd
->alb_count
);
9970 update_rq_clock(busiest_rq
);
9972 p
= detach_one_task(&env
);
9974 schedstat_inc(sd
->alb_pushed
);
9975 /* Active balancing done, reset the failure counter. */
9976 sd
->nr_balance_failed
= 0;
9978 schedstat_inc(sd
->alb_failed
);
9983 busiest_rq
->active_balance
= 0;
9984 rq_unlock(busiest_rq
, &rf
);
9987 attach_one_task(target_rq
, p
);
9994 static DEFINE_SPINLOCK(balancing
);
9997 * Scale the max load_balance interval with the number of CPUs in the system.
9998 * This trades load-balance latency on larger machines for less cross talk.
10000 void update_max_interval(void)
10002 max_load_balance_interval
= HZ
*num_online_cpus()/10;
10006 * It checks each scheduling domain to see if it is due to be balanced,
10007 * and initiates a balancing operation if so.
10009 * Balancing parameters are set up in init_sched_domains.
10011 static void rebalance_domains(struct rq
*rq
, enum cpu_idle_type idle
)
10013 int continue_balancing
= 1;
10015 int busy
= idle
!= CPU_IDLE
&& !sched_idle_cpu(cpu
);
10016 unsigned long interval
;
10017 struct sched_domain
*sd
;
10018 /* Earliest time when we have to do rebalance again */
10019 unsigned long next_balance
= jiffies
+ 60*HZ
;
10020 int update_next_balance
= 0;
10021 int need_serialize
, need_decay
= 0;
10025 for_each_domain(cpu
, sd
) {
10027 * Decay the newidle max times here because this is a regular
10028 * visit to all the domains. Decay ~1% per second.
10030 if (time_after(jiffies
, sd
->next_decay_max_lb_cost
)) {
10031 sd
->max_newidle_lb_cost
=
10032 (sd
->max_newidle_lb_cost
* 253) / 256;
10033 sd
->next_decay_max_lb_cost
= jiffies
+ HZ
;
10036 max_cost
+= sd
->max_newidle_lb_cost
;
10039 * Stop the load balance at this level. There is another
10040 * CPU in our sched group which is doing load balancing more
10043 if (!continue_balancing
) {
10049 interval
= get_sd_balance_interval(sd
, busy
);
10051 need_serialize
= sd
->flags
& SD_SERIALIZE
;
10052 if (need_serialize
) {
10053 if (!spin_trylock(&balancing
))
10057 if (time_after_eq(jiffies
, sd
->last_balance
+ interval
)) {
10058 if (load_balance(cpu
, rq
, sd
, idle
, &continue_balancing
)) {
10060 * The LBF_DST_PINNED logic could have changed
10061 * env->dst_cpu, so we can't know our idle
10062 * state even if we migrated tasks. Update it.
10064 idle
= idle_cpu(cpu
) ? CPU_IDLE
: CPU_NOT_IDLE
;
10065 busy
= idle
!= CPU_IDLE
&& !sched_idle_cpu(cpu
);
10067 sd
->last_balance
= jiffies
;
10068 interval
= get_sd_balance_interval(sd
, busy
);
10070 if (need_serialize
)
10071 spin_unlock(&balancing
);
10073 if (time_after(next_balance
, sd
->last_balance
+ interval
)) {
10074 next_balance
= sd
->last_balance
+ interval
;
10075 update_next_balance
= 1;
10080 * Ensure the rq-wide value also decays but keep it at a
10081 * reasonable floor to avoid funnies with rq->avg_idle.
10083 rq
->max_idle_balance_cost
=
10084 max((u64
)sysctl_sched_migration_cost
, max_cost
);
10089 * next_balance will be updated only when there is a need.
10090 * When the cpu is attached to null domain for ex, it will not be
10093 if (likely(update_next_balance
))
10094 rq
->next_balance
= next_balance
;
10098 static inline int on_null_domain(struct rq
*rq
)
10100 return unlikely(!rcu_dereference_sched(rq
->sd
));
10103 #ifdef CONFIG_NO_HZ_COMMON
10105 * idle load balancing details
10106 * - When one of the busy CPUs notice that there may be an idle rebalancing
10107 * needed, they will kick the idle load balancer, which then does idle
10108 * load balancing for all the idle CPUs.
10109 * - HK_FLAG_MISC CPUs are used for this task, because HK_FLAG_SCHED not set
10113 static inline int find_new_ilb(void)
10117 for_each_cpu_and(ilb
, nohz
.idle_cpus_mask
,
10118 housekeeping_cpumask(HK_FLAG_MISC
)) {
10120 if (ilb
== smp_processor_id())
10131 * Kick a CPU to do the nohz balancing, if it is time for it. We pick any
10132 * idle CPU in the HK_FLAG_MISC housekeeping set (if there is one).
10134 static void kick_ilb(unsigned int flags
)
10139 * Increase nohz.next_balance only when if full ilb is triggered but
10140 * not if we only update stats.
10142 if (flags
& NOHZ_BALANCE_KICK
)
10143 nohz
.next_balance
= jiffies
+1;
10145 ilb_cpu
= find_new_ilb();
10147 if (ilb_cpu
>= nr_cpu_ids
)
10151 * Access to rq::nohz_csd is serialized by NOHZ_KICK_MASK; he who sets
10152 * the first flag owns it; cleared by nohz_csd_func().
10154 flags
= atomic_fetch_or(flags
, nohz_flags(ilb_cpu
));
10155 if (flags
& NOHZ_KICK_MASK
)
10159 * This way we generate an IPI on the target CPU which
10160 * is idle. And the softirq performing nohz idle load balance
10161 * will be run before returning from the IPI.
10163 smp_call_function_single_async(ilb_cpu
, &cpu_rq(ilb_cpu
)->nohz_csd
);
10167 * Current decision point for kicking the idle load balancer in the presence
10168 * of idle CPUs in the system.
10170 static void nohz_balancer_kick(struct rq
*rq
)
10172 unsigned long now
= jiffies
;
10173 struct sched_domain_shared
*sds
;
10174 struct sched_domain
*sd
;
10175 int nr_busy
, i
, cpu
= rq
->cpu
;
10176 unsigned int flags
= 0;
10178 if (unlikely(rq
->idle_balance
))
10182 * We may be recently in ticked or tickless idle mode. At the first
10183 * busy tick after returning from idle, we will update the busy stats.
10185 nohz_balance_exit_idle(rq
);
10188 * None are in tickless mode and hence no need for NOHZ idle load
10191 if (likely(!atomic_read(&nohz
.nr_cpus
)))
10194 if (READ_ONCE(nohz
.has_blocked
) &&
10195 time_after(now
, READ_ONCE(nohz
.next_blocked
)))
10196 flags
= NOHZ_STATS_KICK
;
10198 if (time_before(now
, nohz
.next_balance
))
10201 if (rq
->nr_running
>= 2) {
10202 flags
= NOHZ_KICK_MASK
;
10208 sd
= rcu_dereference(rq
->sd
);
10211 * If there's a CFS task and the current CPU has reduced
10212 * capacity; kick the ILB to see if there's a better CPU to run
10215 if (rq
->cfs
.h_nr_running
>= 1 && check_cpu_capacity(rq
, sd
)) {
10216 flags
= NOHZ_KICK_MASK
;
10221 sd
= rcu_dereference(per_cpu(sd_asym_packing
, cpu
));
10224 * When ASYM_PACKING; see if there's a more preferred CPU
10225 * currently idle; in which case, kick the ILB to move tasks
10228 for_each_cpu_and(i
, sched_domain_span(sd
), nohz
.idle_cpus_mask
) {
10229 if (sched_asym_prefer(i
, cpu
)) {
10230 flags
= NOHZ_KICK_MASK
;
10236 sd
= rcu_dereference(per_cpu(sd_asym_cpucapacity
, cpu
));
10239 * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
10240 * to run the misfit task on.
10242 if (check_misfit_status(rq
, sd
)) {
10243 flags
= NOHZ_KICK_MASK
;
10248 * For asymmetric systems, we do not want to nicely balance
10249 * cache use, instead we want to embrace asymmetry and only
10250 * ensure tasks have enough CPU capacity.
10252 * Skip the LLC logic because it's not relevant in that case.
10257 sds
= rcu_dereference(per_cpu(sd_llc_shared
, cpu
));
10260 * If there is an imbalance between LLC domains (IOW we could
10261 * increase the overall cache use), we need some less-loaded LLC
10262 * domain to pull some load. Likewise, we may need to spread
10263 * load within the current LLC domain (e.g. packed SMT cores but
10264 * other CPUs are idle). We can't really know from here how busy
10265 * the others are - so just get a nohz balance going if it looks
10266 * like this LLC domain has tasks we could move.
10268 nr_busy
= atomic_read(&sds
->nr_busy_cpus
);
10270 flags
= NOHZ_KICK_MASK
;
10281 static void set_cpu_sd_state_busy(int cpu
)
10283 struct sched_domain
*sd
;
10286 sd
= rcu_dereference(per_cpu(sd_llc
, cpu
));
10288 if (!sd
|| !sd
->nohz_idle
)
10292 atomic_inc(&sd
->shared
->nr_busy_cpus
);
10297 void nohz_balance_exit_idle(struct rq
*rq
)
10299 SCHED_WARN_ON(rq
!= this_rq());
10301 if (likely(!rq
->nohz_tick_stopped
))
10304 rq
->nohz_tick_stopped
= 0;
10305 cpumask_clear_cpu(rq
->cpu
, nohz
.idle_cpus_mask
);
10306 atomic_dec(&nohz
.nr_cpus
);
10308 set_cpu_sd_state_busy(rq
->cpu
);
10311 static void set_cpu_sd_state_idle(int cpu
)
10313 struct sched_domain
*sd
;
10316 sd
= rcu_dereference(per_cpu(sd_llc
, cpu
));
10318 if (!sd
|| sd
->nohz_idle
)
10322 atomic_dec(&sd
->shared
->nr_busy_cpus
);
10328 * This routine will record that the CPU is going idle with tick stopped.
10329 * This info will be used in performing idle load balancing in the future.
10331 void nohz_balance_enter_idle(int cpu
)
10333 struct rq
*rq
= cpu_rq(cpu
);
10335 SCHED_WARN_ON(cpu
!= smp_processor_id());
10337 /* If this CPU is going down, then nothing needs to be done: */
10338 if (!cpu_active(cpu
))
10341 /* Spare idle load balancing on CPUs that don't want to be disturbed: */
10342 if (!housekeeping_cpu(cpu
, HK_FLAG_SCHED
))
10346 * Can be set safely without rq->lock held
10347 * If a clear happens, it will have evaluated last additions because
10348 * rq->lock is held during the check and the clear
10350 rq
->has_blocked_load
= 1;
10353 * The tick is still stopped but load could have been added in the
10354 * meantime. We set the nohz.has_blocked flag to trig a check of the
10355 * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
10356 * of nohz.has_blocked can only happen after checking the new load
10358 if (rq
->nohz_tick_stopped
)
10361 /* If we're a completely isolated CPU, we don't play: */
10362 if (on_null_domain(rq
))
10365 rq
->nohz_tick_stopped
= 1;
10367 cpumask_set_cpu(cpu
, nohz
.idle_cpus_mask
);
10368 atomic_inc(&nohz
.nr_cpus
);
10371 * Ensures that if nohz_idle_balance() fails to observe our
10372 * @idle_cpus_mask store, it must observe the @has_blocked
10375 smp_mb__after_atomic();
10377 set_cpu_sd_state_idle(cpu
);
10381 * Each time a cpu enter idle, we assume that it has blocked load and
10382 * enable the periodic update of the load of idle cpus
10384 WRITE_ONCE(nohz
.has_blocked
, 1);
10387 static bool update_nohz_stats(struct rq
*rq
)
10389 unsigned int cpu
= rq
->cpu
;
10391 if (!rq
->has_blocked_load
)
10394 if (!cpumask_test_cpu(cpu
, nohz
.idle_cpus_mask
))
10397 if (!time_after(jiffies
, READ_ONCE(rq
->last_blocked_load_update_tick
)))
10400 update_blocked_averages(cpu
);
10402 return rq
->has_blocked_load
;
10406 * Internal function that runs load balance for all idle cpus. The load balance
10407 * can be a simple update of blocked load or a complete load balance with
10408 * tasks movement depending of flags.
10410 static void _nohz_idle_balance(struct rq
*this_rq
, unsigned int flags
,
10411 enum cpu_idle_type idle
)
10413 /* Earliest time when we have to do rebalance again */
10414 unsigned long now
= jiffies
;
10415 unsigned long next_balance
= now
+ 60*HZ
;
10416 bool has_blocked_load
= false;
10417 int update_next_balance
= 0;
10418 int this_cpu
= this_rq
->cpu
;
10422 SCHED_WARN_ON((flags
& NOHZ_KICK_MASK
) == NOHZ_BALANCE_KICK
);
10425 * We assume there will be no idle load after this update and clear
10426 * the has_blocked flag. If a cpu enters idle in the mean time, it will
10427 * set the has_blocked flag and trig another update of idle load.
10428 * Because a cpu that becomes idle, is added to idle_cpus_mask before
10429 * setting the flag, we are sure to not clear the state and not
10430 * check the load of an idle cpu.
10432 WRITE_ONCE(nohz
.has_blocked
, 0);
10435 * Ensures that if we miss the CPU, we must see the has_blocked
10436 * store from nohz_balance_enter_idle().
10441 * Start with the next CPU after this_cpu so we will end with this_cpu and let a
10442 * chance for other idle cpu to pull load.
10444 for_each_cpu_wrap(balance_cpu
, nohz
.idle_cpus_mask
, this_cpu
+1) {
10445 if (!idle_cpu(balance_cpu
))
10449 * If this CPU gets work to do, stop the load balancing
10450 * work being done for other CPUs. Next load
10451 * balancing owner will pick it up.
10453 if (need_resched()) {
10454 has_blocked_load
= true;
10458 rq
= cpu_rq(balance_cpu
);
10460 has_blocked_load
|= update_nohz_stats(rq
);
10463 * If time for next balance is due,
10466 if (time_after_eq(jiffies
, rq
->next_balance
)) {
10467 struct rq_flags rf
;
10469 rq_lock_irqsave(rq
, &rf
);
10470 update_rq_clock(rq
);
10471 rq_unlock_irqrestore(rq
, &rf
);
10473 if (flags
& NOHZ_BALANCE_KICK
)
10474 rebalance_domains(rq
, CPU_IDLE
);
10477 if (time_after(next_balance
, rq
->next_balance
)) {
10478 next_balance
= rq
->next_balance
;
10479 update_next_balance
= 1;
10484 * next_balance will be updated only when there is a need.
10485 * When the CPU is attached to null domain for ex, it will not be
10488 if (likely(update_next_balance
))
10489 nohz
.next_balance
= next_balance
;
10491 WRITE_ONCE(nohz
.next_blocked
,
10492 now
+ msecs_to_jiffies(LOAD_AVG_PERIOD
));
10495 /* There is still blocked load, enable periodic update */
10496 if (has_blocked_load
)
10497 WRITE_ONCE(nohz
.has_blocked
, 1);
10501 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
10502 * rebalancing for all the cpus for whom scheduler ticks are stopped.
10504 static bool nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
)
10506 unsigned int flags
= this_rq
->nohz_idle_balance
;
10511 this_rq
->nohz_idle_balance
= 0;
10513 if (idle
!= CPU_IDLE
)
10516 _nohz_idle_balance(this_rq
, flags
, idle
);
10522 * Check if we need to run the ILB for updating blocked load before entering
10525 void nohz_run_idle_balance(int cpu
)
10527 unsigned int flags
;
10529 flags
= atomic_fetch_andnot(NOHZ_NEWILB_KICK
, nohz_flags(cpu
));
10532 * Update the blocked load only if no SCHED_SOFTIRQ is about to happen
10533 * (ie NOHZ_STATS_KICK set) and will do the same.
10535 if ((flags
== NOHZ_NEWILB_KICK
) && !need_resched())
10536 _nohz_idle_balance(cpu_rq(cpu
), NOHZ_STATS_KICK
, CPU_IDLE
);
10539 static void nohz_newidle_balance(struct rq
*this_rq
)
10541 int this_cpu
= this_rq
->cpu
;
10544 * This CPU doesn't want to be disturbed by scheduler
10547 if (!housekeeping_cpu(this_cpu
, HK_FLAG_SCHED
))
10550 /* Will wake up very soon. No time for doing anything else*/
10551 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
)
10554 /* Don't need to update blocked load of idle CPUs*/
10555 if (!READ_ONCE(nohz
.has_blocked
) ||
10556 time_before(jiffies
, READ_ONCE(nohz
.next_blocked
)))
10560 * Set the need to trigger ILB in order to update blocked load
10561 * before entering idle state.
10563 atomic_or(NOHZ_NEWILB_KICK
, nohz_flags(this_cpu
));
10566 #else /* !CONFIG_NO_HZ_COMMON */
10567 static inline void nohz_balancer_kick(struct rq
*rq
) { }
10569 static inline bool nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
)
10574 static inline void nohz_newidle_balance(struct rq
*this_rq
) { }
10575 #endif /* CONFIG_NO_HZ_COMMON */
10578 * newidle_balance is called by schedule() if this_cpu is about to become
10579 * idle. Attempts to pull tasks from other CPUs.
10582 * < 0 - we released the lock and there are !fair tasks present
10583 * 0 - failed, no new tasks
10584 * > 0 - success, new (fair) tasks present
10586 static int newidle_balance(struct rq
*this_rq
, struct rq_flags
*rf
)
10588 unsigned long next_balance
= jiffies
+ HZ
;
10589 int this_cpu
= this_rq
->cpu
;
10590 struct sched_domain
*sd
;
10591 int pulled_task
= 0;
10594 update_misfit_status(NULL
, this_rq
);
10596 * We must set idle_stamp _before_ calling idle_balance(), such that we
10597 * measure the duration of idle_balance() as idle time.
10599 this_rq
->idle_stamp
= rq_clock(this_rq
);
10602 * Do not pull tasks towards !active CPUs...
10604 if (!cpu_active(this_cpu
))
10608 * This is OK, because current is on_cpu, which avoids it being picked
10609 * for load-balance and preemption/IRQs are still disabled avoiding
10610 * further scheduler activity on it and we're being very careful to
10611 * re-start the picking loop.
10613 rq_unpin_lock(this_rq
, rf
);
10615 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
||
10616 !READ_ONCE(this_rq
->rd
->overload
)) {
10619 sd
= rcu_dereference_check_sched_domain(this_rq
->sd
);
10621 update_next_balance(sd
, &next_balance
);
10627 raw_spin_unlock(&this_rq
->lock
);
10629 update_blocked_averages(this_cpu
);
10631 for_each_domain(this_cpu
, sd
) {
10632 int continue_balancing
= 1;
10633 u64 t0
, domain_cost
;
10635 if (this_rq
->avg_idle
< curr_cost
+ sd
->max_newidle_lb_cost
) {
10636 update_next_balance(sd
, &next_balance
);
10640 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
10641 t0
= sched_clock_cpu(this_cpu
);
10643 pulled_task
= load_balance(this_cpu
, this_rq
,
10644 sd
, CPU_NEWLY_IDLE
,
10645 &continue_balancing
);
10647 domain_cost
= sched_clock_cpu(this_cpu
) - t0
;
10648 if (domain_cost
> sd
->max_newidle_lb_cost
)
10649 sd
->max_newidle_lb_cost
= domain_cost
;
10651 curr_cost
+= domain_cost
;
10654 update_next_balance(sd
, &next_balance
);
10657 * Stop searching for tasks to pull if there are
10658 * now runnable tasks on this rq.
10660 if (pulled_task
|| this_rq
->nr_running
> 0)
10665 raw_spin_lock(&this_rq
->lock
);
10667 if (curr_cost
> this_rq
->max_idle_balance_cost
)
10668 this_rq
->max_idle_balance_cost
= curr_cost
;
10671 * While browsing the domains, we released the rq lock, a task could
10672 * have been enqueued in the meantime. Since we're not going idle,
10673 * pretend we pulled a task.
10675 if (this_rq
->cfs
.h_nr_running
&& !pulled_task
)
10678 /* Is there a task of a high priority class? */
10679 if (this_rq
->nr_running
!= this_rq
->cfs
.h_nr_running
)
10683 /* Move the next balance forward */
10684 if (time_after(this_rq
->next_balance
, next_balance
))
10685 this_rq
->next_balance
= next_balance
;
10688 this_rq
->idle_stamp
= 0;
10690 nohz_newidle_balance(this_rq
);
10692 rq_repin_lock(this_rq
, rf
);
10694 return pulled_task
;
10698 * run_rebalance_domains is triggered when needed from the scheduler tick.
10699 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
10701 static __latent_entropy
void run_rebalance_domains(struct softirq_action
*h
)
10703 struct rq
*this_rq
= this_rq();
10704 enum cpu_idle_type idle
= this_rq
->idle_balance
?
10705 CPU_IDLE
: CPU_NOT_IDLE
;
10708 * If this CPU has a pending nohz_balance_kick, then do the
10709 * balancing on behalf of the other idle CPUs whose ticks are
10710 * stopped. Do nohz_idle_balance *before* rebalance_domains to
10711 * give the idle CPUs a chance to load balance. Else we may
10712 * load balance only within the local sched_domain hierarchy
10713 * and abort nohz_idle_balance altogether if we pull some load.
10715 if (nohz_idle_balance(this_rq
, idle
))
10718 /* normal load balance */
10719 update_blocked_averages(this_rq
->cpu
);
10720 rebalance_domains(this_rq
, idle
);
10724 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
10726 void trigger_load_balance(struct rq
*rq
)
10729 * Don't need to rebalance while attached to NULL domain or
10730 * runqueue CPU is not active
10732 if (unlikely(on_null_domain(rq
) || !cpu_active(cpu_of(rq
))))
10735 if (time_after_eq(jiffies
, rq
->next_balance
))
10736 raise_softirq(SCHED_SOFTIRQ
);
10738 nohz_balancer_kick(rq
);
10741 static void rq_online_fair(struct rq
*rq
)
10745 update_runtime_enabled(rq
);
10748 static void rq_offline_fair(struct rq
*rq
)
10752 /* Ensure any throttled groups are reachable by pick_next_task */
10753 unthrottle_offline_cfs_rqs(rq
);
10756 #endif /* CONFIG_SMP */
10759 * scheduler tick hitting a task of our scheduling class.
10761 * NOTE: This function can be called remotely by the tick offload that
10762 * goes along full dynticks. Therefore no local assumption can be made
10763 * and everything must be accessed through the @rq and @curr passed in
10766 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
10768 struct cfs_rq
*cfs_rq
;
10769 struct sched_entity
*se
= &curr
->se
;
10771 for_each_sched_entity(se
) {
10772 cfs_rq
= cfs_rq_of(se
);
10773 entity_tick(cfs_rq
, se
, queued
);
10776 if (static_branch_unlikely(&sched_numa_balancing
))
10777 task_tick_numa(rq
, curr
);
10779 update_misfit_status(curr
, rq
);
10780 update_overutilized_status(task_rq(curr
));
10784 * called on fork with the child task as argument from the parent's context
10785 * - child not yet on the tasklist
10786 * - preemption disabled
10788 static void task_fork_fair(struct task_struct
*p
)
10790 struct cfs_rq
*cfs_rq
;
10791 struct sched_entity
*se
= &p
->se
, *curr
;
10792 struct rq
*rq
= this_rq();
10793 struct rq_flags rf
;
10796 update_rq_clock(rq
);
10798 cfs_rq
= task_cfs_rq(current
);
10799 curr
= cfs_rq
->curr
;
10801 update_curr(cfs_rq
);
10802 se
->vruntime
= curr
->vruntime
;
10804 place_entity(cfs_rq
, se
, 1);
10806 if (sysctl_sched_child_runs_first
&& curr
&& entity_before(curr
, se
)) {
10808 * Upon rescheduling, sched_class::put_prev_task() will place
10809 * 'current' within the tree based on its new key value.
10811 swap(curr
->vruntime
, se
->vruntime
);
10815 se
->vruntime
-= cfs_rq
->min_vruntime
;
10816 rq_unlock(rq
, &rf
);
10820 * Priority of the task has changed. Check to see if we preempt
10821 * the current task.
10824 prio_changed_fair(struct rq
*rq
, struct task_struct
*p
, int oldprio
)
10826 if (!task_on_rq_queued(p
))
10829 if (rq
->cfs
.nr_running
== 1)
10833 * Reschedule if we are currently running on this runqueue and
10834 * our priority decreased, or if we are not currently running on
10835 * this runqueue and our priority is higher than the current's
10837 if (task_current(rq
, p
)) {
10838 if (p
->prio
> oldprio
)
10841 check_preempt_curr(rq
, p
, 0);
10844 static inline bool vruntime_normalized(struct task_struct
*p
)
10846 struct sched_entity
*se
= &p
->se
;
10849 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
10850 * the dequeue_entity(.flags=0) will already have normalized the
10857 * When !on_rq, vruntime of the task has usually NOT been normalized.
10858 * But there are some cases where it has already been normalized:
10860 * - A forked child which is waiting for being woken up by
10861 * wake_up_new_task().
10862 * - A task which has been woken up by try_to_wake_up() and
10863 * waiting for actually being woken up by sched_ttwu_pending().
10865 if (!se
->sum_exec_runtime
||
10866 (p
->state
== TASK_WAKING
&& p
->sched_remote_wakeup
))
10872 #ifdef CONFIG_FAIR_GROUP_SCHED
10874 * Propagate the changes of the sched_entity across the tg tree to make it
10875 * visible to the root
10877 static void propagate_entity_cfs_rq(struct sched_entity
*se
)
10879 struct cfs_rq
*cfs_rq
;
10881 /* Start to propagate at parent */
10884 for_each_sched_entity(se
) {
10885 cfs_rq
= cfs_rq_of(se
);
10887 if (cfs_rq_throttled(cfs_rq
))
10890 update_load_avg(cfs_rq
, se
, UPDATE_TG
);
10894 static void propagate_entity_cfs_rq(struct sched_entity
*se
) { }
10897 static void detach_entity_cfs_rq(struct sched_entity
*se
)
10899 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
10901 /* Catch up with the cfs_rq and remove our load when we leave */
10902 update_load_avg(cfs_rq
, se
, 0);
10903 detach_entity_load_avg(cfs_rq
, se
);
10904 update_tg_load_avg(cfs_rq
);
10905 propagate_entity_cfs_rq(se
);
10908 static void attach_entity_cfs_rq(struct sched_entity
*se
)
10910 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
10912 #ifdef CONFIG_FAIR_GROUP_SCHED
10914 * Since the real-depth could have been changed (only FAIR
10915 * class maintain depth value), reset depth properly.
10917 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
10920 /* Synchronize entity with its cfs_rq */
10921 update_load_avg(cfs_rq
, se
, sched_feat(ATTACH_AGE_LOAD
) ? 0 : SKIP_AGE_LOAD
);
10922 attach_entity_load_avg(cfs_rq
, se
);
10923 update_tg_load_avg(cfs_rq
);
10924 propagate_entity_cfs_rq(se
);
10927 static void detach_task_cfs_rq(struct task_struct
*p
)
10929 struct sched_entity
*se
= &p
->se
;
10930 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
10932 if (!vruntime_normalized(p
)) {
10934 * Fix up our vruntime so that the current sleep doesn't
10935 * cause 'unlimited' sleep bonus.
10937 place_entity(cfs_rq
, se
, 0);
10938 se
->vruntime
-= cfs_rq
->min_vruntime
;
10941 detach_entity_cfs_rq(se
);
10944 static void attach_task_cfs_rq(struct task_struct
*p
)
10946 struct sched_entity
*se
= &p
->se
;
10947 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
10949 attach_entity_cfs_rq(se
);
10951 if (!vruntime_normalized(p
))
10952 se
->vruntime
+= cfs_rq
->min_vruntime
;
10955 static void switched_from_fair(struct rq
*rq
, struct task_struct
*p
)
10957 detach_task_cfs_rq(p
);
10960 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
)
10962 attach_task_cfs_rq(p
);
10964 if (task_on_rq_queued(p
)) {
10966 * We were most likely switched from sched_rt, so
10967 * kick off the schedule if running, otherwise just see
10968 * if we can still preempt the current task.
10970 if (task_current(rq
, p
))
10973 check_preempt_curr(rq
, p
, 0);
10977 /* Account for a task changing its policy or group.
10979 * This routine is mostly called to set cfs_rq->curr field when a task
10980 * migrates between groups/classes.
10982 static void set_next_task_fair(struct rq
*rq
, struct task_struct
*p
, bool first
)
10984 struct sched_entity
*se
= &p
->se
;
10987 if (task_on_rq_queued(p
)) {
10989 * Move the next running task to the front of the list, so our
10990 * cfs_tasks list becomes MRU one.
10992 list_move(&se
->group_node
, &rq
->cfs_tasks
);
10996 for_each_sched_entity(se
) {
10997 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
10999 set_next_entity(cfs_rq
, se
);
11000 /* ensure bandwidth has been allocated on our new cfs_rq */
11001 account_cfs_rq_runtime(cfs_rq
, 0);
11005 void init_cfs_rq(struct cfs_rq
*cfs_rq
)
11007 cfs_rq
->tasks_timeline
= RB_ROOT_CACHED
;
11008 cfs_rq
->min_vruntime
= (u64
)(-(1LL << 20));
11009 #ifndef CONFIG_64BIT
11010 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
11013 raw_spin_lock_init(&cfs_rq
->removed
.lock
);
11017 #ifdef CONFIG_FAIR_GROUP_SCHED
11018 static void task_set_group_fair(struct task_struct
*p
)
11020 struct sched_entity
*se
= &p
->se
;
11022 set_task_rq(p
, task_cpu(p
));
11023 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
11026 static void task_move_group_fair(struct task_struct
*p
)
11028 detach_task_cfs_rq(p
);
11029 set_task_rq(p
, task_cpu(p
));
11032 /* Tell se's cfs_rq has been changed -- migrated */
11033 p
->se
.avg
.last_update_time
= 0;
11035 attach_task_cfs_rq(p
);
11038 static void task_change_group_fair(struct task_struct
*p
, int type
)
11041 case TASK_SET_GROUP
:
11042 task_set_group_fair(p
);
11045 case TASK_MOVE_GROUP
:
11046 task_move_group_fair(p
);
11051 void free_fair_sched_group(struct task_group
*tg
)
11055 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg
));
11057 for_each_possible_cpu(i
) {
11059 kfree(tg
->cfs_rq
[i
]);
11068 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
11070 struct sched_entity
*se
;
11071 struct cfs_rq
*cfs_rq
;
11074 tg
->cfs_rq
= kcalloc(nr_cpu_ids
, sizeof(cfs_rq
), GFP_KERNEL
);
11077 tg
->se
= kcalloc(nr_cpu_ids
, sizeof(se
), GFP_KERNEL
);
11081 tg
->shares
= NICE_0_LOAD
;
11083 init_cfs_bandwidth(tg_cfs_bandwidth(tg
));
11085 for_each_possible_cpu(i
) {
11086 cfs_rq
= kzalloc_node(sizeof(struct cfs_rq
),
11087 GFP_KERNEL
, cpu_to_node(i
));
11091 se
= kzalloc_node(sizeof(struct sched_entity
),
11092 GFP_KERNEL
, cpu_to_node(i
));
11096 init_cfs_rq(cfs_rq
);
11097 init_tg_cfs_entry(tg
, cfs_rq
, se
, i
, parent
->se
[i
]);
11098 init_entity_runnable_average(se
);
11109 void online_fair_sched_group(struct task_group
*tg
)
11111 struct sched_entity
*se
;
11112 struct rq_flags rf
;
11116 for_each_possible_cpu(i
) {
11119 rq_lock_irq(rq
, &rf
);
11120 update_rq_clock(rq
);
11121 attach_entity_cfs_rq(se
);
11122 sync_throttle(tg
, i
);
11123 rq_unlock_irq(rq
, &rf
);
11127 void unregister_fair_sched_group(struct task_group
*tg
)
11129 unsigned long flags
;
11133 for_each_possible_cpu(cpu
) {
11135 remove_entity_load_avg(tg
->se
[cpu
]);
11138 * Only empty task groups can be destroyed; so we can speculatively
11139 * check on_list without danger of it being re-added.
11141 if (!tg
->cfs_rq
[cpu
]->on_list
)
11146 raw_spin_lock_irqsave(&rq
->lock
, flags
);
11147 list_del_leaf_cfs_rq(tg
->cfs_rq
[cpu
]);
11148 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
11152 void init_tg_cfs_entry(struct task_group
*tg
, struct cfs_rq
*cfs_rq
,
11153 struct sched_entity
*se
, int cpu
,
11154 struct sched_entity
*parent
)
11156 struct rq
*rq
= cpu_rq(cpu
);
11160 init_cfs_rq_runtime(cfs_rq
);
11162 tg
->cfs_rq
[cpu
] = cfs_rq
;
11165 /* se could be NULL for root_task_group */
11170 se
->cfs_rq
= &rq
->cfs
;
11173 se
->cfs_rq
= parent
->my_q
;
11174 se
->depth
= parent
->depth
+ 1;
11178 /* guarantee group entities always have weight */
11179 update_load_set(&se
->load
, NICE_0_LOAD
);
11180 se
->parent
= parent
;
11183 static DEFINE_MUTEX(shares_mutex
);
11185 int sched_group_set_shares(struct task_group
*tg
, unsigned long shares
)
11190 * We can't change the weight of the root cgroup.
11195 shares
= clamp(shares
, scale_load(MIN_SHARES
), scale_load(MAX_SHARES
));
11197 mutex_lock(&shares_mutex
);
11198 if (tg
->shares
== shares
)
11201 tg
->shares
= shares
;
11202 for_each_possible_cpu(i
) {
11203 struct rq
*rq
= cpu_rq(i
);
11204 struct sched_entity
*se
= tg
->se
[i
];
11205 struct rq_flags rf
;
11207 /* Propagate contribution to hierarchy */
11208 rq_lock_irqsave(rq
, &rf
);
11209 update_rq_clock(rq
);
11210 for_each_sched_entity(se
) {
11211 update_load_avg(cfs_rq_of(se
), se
, UPDATE_TG
);
11212 update_cfs_group(se
);
11214 rq_unlock_irqrestore(rq
, &rf
);
11218 mutex_unlock(&shares_mutex
);
11221 #else /* CONFIG_FAIR_GROUP_SCHED */
11223 void free_fair_sched_group(struct task_group
*tg
) { }
11225 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
11230 void online_fair_sched_group(struct task_group
*tg
) { }
11232 void unregister_fair_sched_group(struct task_group
*tg
) { }
11234 #endif /* CONFIG_FAIR_GROUP_SCHED */
11237 static unsigned int get_rr_interval_fair(struct rq
*rq
, struct task_struct
*task
)
11239 struct sched_entity
*se
= &task
->se
;
11240 unsigned int rr_interval
= 0;
11243 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
11246 if (rq
->cfs
.load
.weight
)
11247 rr_interval
= NS_TO_JIFFIES(sched_slice(cfs_rq_of(se
), se
));
11249 return rr_interval
;
11253 * All the scheduling class methods:
11255 DEFINE_SCHED_CLASS(fair
) = {
11257 .enqueue_task
= enqueue_task_fair
,
11258 .dequeue_task
= dequeue_task_fair
,
11259 .yield_task
= yield_task_fair
,
11260 .yield_to_task
= yield_to_task_fair
,
11262 .check_preempt_curr
= check_preempt_wakeup
,
11264 .pick_next_task
= __pick_next_task_fair
,
11265 .put_prev_task
= put_prev_task_fair
,
11266 .set_next_task
= set_next_task_fair
,
11269 .balance
= balance_fair
,
11270 .select_task_rq
= select_task_rq_fair
,
11271 .migrate_task_rq
= migrate_task_rq_fair
,
11273 .rq_online
= rq_online_fair
,
11274 .rq_offline
= rq_offline_fair
,
11276 .task_dead
= task_dead_fair
,
11277 .set_cpus_allowed
= set_cpus_allowed_common
,
11280 .task_tick
= task_tick_fair
,
11281 .task_fork
= task_fork_fair
,
11283 .prio_changed
= prio_changed_fair
,
11284 .switched_from
= switched_from_fair
,
11285 .switched_to
= switched_to_fair
,
11287 .get_rr_interval
= get_rr_interval_fair
,
11289 .update_curr
= update_curr_fair
,
11291 #ifdef CONFIG_FAIR_GROUP_SCHED
11292 .task_change_group
= task_change_group_fair
,
11295 #ifdef CONFIG_UCLAMP_TASK
11296 .uclamp_enabled
= 1,
11300 #ifdef CONFIG_SCHED_DEBUG
11301 void print_cfs_stats(struct seq_file
*m
, int cpu
)
11303 struct cfs_rq
*cfs_rq
, *pos
;
11306 for_each_leaf_cfs_rq_safe(cpu_rq(cpu
), cfs_rq
, pos
)
11307 print_cfs_rq(m
, cpu
, cfs_rq
);
11311 #ifdef CONFIG_NUMA_BALANCING
11312 void show_numa_stats(struct task_struct
*p
, struct seq_file
*m
)
11315 unsigned long tsf
= 0, tpf
= 0, gsf
= 0, gpf
= 0;
11316 struct numa_group
*ng
;
11319 ng
= rcu_dereference(p
->numa_group
);
11320 for_each_online_node(node
) {
11321 if (p
->numa_faults
) {
11322 tsf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 0)];
11323 tpf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
11326 gsf
= ng
->faults
[task_faults_idx(NUMA_MEM
, node
, 0)],
11327 gpf
= ng
->faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
11329 print_numa_stats(m
, node
, tsf
, tpf
, gsf
, gpf
);
11333 #endif /* CONFIG_NUMA_BALANCING */
11334 #endif /* CONFIG_SCHED_DEBUG */
11336 __init
void init_sched_fair_class(void)
11339 open_softirq(SCHED_SOFTIRQ
, run_rebalance_domains
);
11341 #ifdef CONFIG_NO_HZ_COMMON
11342 nohz
.next_balance
= jiffies
;
11343 nohz
.next_blocked
= jiffies
;
11344 zalloc_cpumask_var(&nohz
.idle_cpus_mask
, GFP_NOWAIT
);
11351 * Helper functions to facilitate extracting info from tracepoints.
11354 const struct sched_avg
*sched_trace_cfs_rq_avg(struct cfs_rq
*cfs_rq
)
11357 return cfs_rq
? &cfs_rq
->avg
: NULL
;
11362 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_avg
);
11364 char *sched_trace_cfs_rq_path(struct cfs_rq
*cfs_rq
, char *str
, int len
)
11368 strlcpy(str
, "(null)", len
);
11373 cfs_rq_tg_path(cfs_rq
, str
, len
);
11376 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_path
);
11378 int sched_trace_cfs_rq_cpu(struct cfs_rq
*cfs_rq
)
11380 return cfs_rq
? cpu_of(rq_of(cfs_rq
)) : -1;
11382 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_cpu
);
11384 const struct sched_avg
*sched_trace_rq_avg_rt(struct rq
*rq
)
11387 return rq
? &rq
->avg_rt
: NULL
;
11392 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_rt
);
11394 const struct sched_avg
*sched_trace_rq_avg_dl(struct rq
*rq
)
11397 return rq
? &rq
->avg_dl
: NULL
;
11402 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_dl
);
11404 const struct sched_avg
*sched_trace_rq_avg_irq(struct rq
*rq
)
11406 #if defined(CONFIG_SMP) && defined(CONFIG_HAVE_SCHED_AVG_IRQ)
11407 return rq
? &rq
->avg_irq
: NULL
;
11412 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_irq
);
11414 int sched_trace_rq_cpu(struct rq
*rq
)
11416 return rq
? cpu_of(rq
) : -1;
11418 EXPORT_SYMBOL_GPL(sched_trace_rq_cpu
);
11420 int sched_trace_rq_cpu_capacity(struct rq
*rq
)
11426 SCHED_CAPACITY_SCALE
11430 EXPORT_SYMBOL_GPL(sched_trace_rq_cpu_capacity
);
11432 const struct cpumask
*sched_trace_rd_span(struct root_domain
*rd
)
11435 return rd
? rd
->span
: NULL
;
11440 EXPORT_SYMBOL_GPL(sched_trace_rd_span
);
11442 int sched_trace_rq_nr_running(struct rq
*rq
)
11444 return rq
? rq
->nr_running
: -1;
11446 EXPORT_SYMBOL_GPL(sched_trace_rq_nr_running
);